github/testdata/testoutput1

# This set of tests is for features that are compatible with all versions of
# Perl >= 5.10, in non-UTF mode. It should run clean for the 8-bit, 16-bit, and
# 32-bit PCRE libraries, and also using the perltest.sh script.

# WARNING: Use only / as the pattern delimiter. Although pcre2test supports
# a number of delimiters, all those other than / give problems with the
# perltest.sh script.
    
#forbid_utf
#newline_default lf any anycrlf
#perltest

/the quick brown fox/
    the quick brown fox
 0: the quick brown fox
    What do you know about the quick brown fox?
 0: the quick brown fox
\= Expect no match
    The quick brown FOX
No match
    What do you know about THE QUICK BROWN FOX?
No match

/The quick brown fox/i
    the quick brown fox
 0: the quick brown fox
    The quick brown FOX
 0: The quick brown FOX
    What do you know about the quick brown fox?
 0: the quick brown fox
    What do you know about THE QUICK BROWN FOX?
 0: THE QUICK BROWN FOX

/abcd\t\n\r\f\a\e\071\x3b\$\\\?caxyz/
    abcd\t\n\r\f\a\e9;\$\\?caxyz
 0: abcd\x09\x0a\x0d\x0c\x07\x1b9;$\?caxyz

/a*abc?xyz+pqr{3}ab{2,}xy{4,5}pq{0,6}AB{0,}zz/
    abxyzpqrrrabbxyyyypqAzz
 0: abxyzpqrrrabbxyyyypqAzz
    abxyzpqrrrabbxyyyypqAzz
 0: abxyzpqrrrabbxyyyypqAzz
    aabxyzpqrrrabbxyyyypqAzz
 0: aabxyzpqrrrabbxyyyypqAzz
    aaabxyzpqrrrabbxyyyypqAzz
 0: aaabxyzpqrrrabbxyyyypqAzz
    aaaabxyzpqrrrabbxyyyypqAzz
 0: aaaabxyzpqrrrabbxyyyypqAzz
    abcxyzpqrrrabbxyyyypqAzz
 0: abcxyzpqrrrabbxyyyypqAzz
    aabcxyzpqrrrabbxyyyypqAzz
 0: aabcxyzpqrrrabbxyyyypqAzz
    aaabcxyzpqrrrabbxyyyypAzz
 0: aaabcxyzpqrrrabbxyyyypAzz
    aaabcxyzpqrrrabbxyyyypqAzz
 0: aaabcxyzpqrrrabbxyyyypqAzz
    aaabcxyzpqrrrabbxyyyypqqAzz
 0: aaabcxyzpqrrrabbxyyyypqqAzz
    aaabcxyzpqrrrabbxyyyypqqqAzz
 0: aaabcxyzpqrrrabbxyyyypqqqAzz
    aaabcxyzpqrrrabbxyyyypqqqqAzz
 0: aaabcxyzpqrrrabbxyyyypqqqqAzz
    aaabcxyzpqrrrabbxyyyypqqqqqAzz
 0: aaabcxyzpqrrrabbxyyyypqqqqqAzz
    aaabcxyzpqrrrabbxyyyypqqqqqqAzz
 0: aaabcxyzpqrrrabbxyyyypqqqqqqAzz
    aaaabcxyzpqrrrabbxyyyypqAzz
 0: aaaabcxyzpqrrrabbxyyyypqAzz
    abxyzzpqrrrabbxyyyypqAzz
 0: abxyzzpqrrrabbxyyyypqAzz
    aabxyzzzpqrrrabbxyyyypqAzz
 0: aabxyzzzpqrrrabbxyyyypqAzz
    aaabxyzzzzpqrrrabbxyyyypqAzz
 0: aaabxyzzzzpqrrrabbxyyyypqAzz
    aaaabxyzzzzpqrrrabbxyyyypqAzz
 0: aaaabxyzzzzpqrrrabbxyyyypqAzz
    abcxyzzpqrrrabbxyyyypqAzz
 0: abcxyzzpqrrrabbxyyyypqAzz
    aabcxyzzzpqrrrabbxyyyypqAzz
 0: aabcxyzzzpqrrrabbxyyyypqAzz
    aaabcxyzzzzpqrrrabbxyyyypqAzz
 0: aaabcxyzzzzpqrrrabbxyyyypqAzz
    aaaabcxyzzzzpqrrrabbxyyyypqAzz
 0: aaaabcxyzzzzpqrrrabbxyyyypqAzz
    aaaabcxyzzzzpqrrrabbbxyyyypqAzz
 0: aaaabcxyzzzzpqrrrabbbxyyyypqAzz
    aaaabcxyzzzzpqrrrabbbxyyyyypqAzz
 0: aaaabcxyzzzzpqrrrabbbxyyyyypqAzz
    aaabcxyzpqrrrabbxyyyypABzz
 0: aaabcxyzpqrrrabbxyyyypABzz
    aaabcxyzpqrrrabbxyyyypABBzz
 0: aaabcxyzpqrrrabbxyyyypABBzz
    >>>aaabxyzpqrrrabbxyyyypqAzz
 0: aaabxyzpqrrrabbxyyyypqAzz
    >aaaabxyzpqrrrabbxyyyypqAzz
 0: aaaabxyzpqrrrabbxyyyypqAzz
    >>>>abcxyzpqrrrabbxyyyypqAzz
 0: abcxyzpqrrrabbxyyyypqAzz
\= Expect no match
    abxyzpqrrabbxyyyypqAzz
No match
    abxyzpqrrrrabbxyyyypqAzz
No match
    abxyzpqrrrabxyyyypqAzz
No match
    aaaabcxyzzzzpqrrrabbbxyyyyyypqAzz
No match
    aaaabcxyzzzzpqrrrabbbxyyypqAzz
No match
    aaabcxyzpqrrrabbxyyyypqqqqqqqAzz
No match

/^(abc){1,2}zz/
    abczz
 0: abczz
 1: abc
    abcabczz
 0: abcabczz
 1: abc
\= Expect no match
    zz
No match
    abcabcabczz
No match
    >>abczz
No match

/^(b+?|a){1,2}?c/
    bc
 0: bc
 1: b
    bbc
 0: bbc
 1: b
    bbbc
 0: bbbc
 1: bb
    bac
 0: bac
 1: a
    bbac
 0: bbac
 1: a
    aac
 0: aac
 1: a
    abbbbbbbbbbbc
 0: abbbbbbbbbbbc
 1: bbbbbbbbbbb
    bbbbbbbbbbbac
 0: bbbbbbbbbbbac
 1: a
\= Expect no match
    aaac
No match
    abbbbbbbbbbbac
No match

/^(b+|a){1,2}c/
    bc
 0: bc
 1: b
    bbc
 0: bbc
 1: bb
    bbbc
 0: bbbc
 1: bbb
    bac
 0: bac
 1: a
    bbac
 0: bbac
 1: a
    aac
 0: aac
 1: a
    abbbbbbbbbbbc
 0: abbbbbbbbbbbc
 1: bbbbbbbbbbb
    bbbbbbbbbbbac
 0: bbbbbbbbbbbac
 1: a
\= Expect no match
    aaac
No match
    abbbbbbbbbbbac
No match

/^(ba|b*){1,2}?bc/
    babc
 0: babc
 1: ba
    bbabc
 0: bbabc
 1: ba
    bababc
 0: bababc
 1: ba
\= Expect no match
    bababbc
No match
    babababc
No match

/^\ca\cA\c[;\c:/
    \x01\x01\e;z
 0: \x01\x01\x1b;z

/^[ab\]cde]/
    athing
 0: a
    bthing
 0: b
    ]thing
 0: ]
    cthing
 0: c
    dthing
 0: d
    ething
 0: e
\= Expect no match
    fthing
No match
    [thing
No match
    \\thing
No match

/^[]cde]/
    ]thing
 0: ]
    cthing
 0: c
    dthing
 0: d
    ething
 0: e
\= Expect no match
    athing
No match
    fthing
No match

/^[^ab\]cde]/
    fthing
 0: f
    [thing
 0: [
    \\thing
 0: \
\= Expect no match
    athing
No match
    bthing
No match
    ]thing
No match
    cthing
No match
    dthing
No match
    ething
No match

/^[^]cde]/
    athing
 0: a
    fthing
 0: f
\= Expect no match
    ]thing
No match
    cthing
No match
    dthing
No match
    ething
No match

/^\�/
    �
 0: \x81

/^�/
    �
 0: \xff

/^[0-9]+$/
    0
 0: 0
    1
 0: 1
    2
 0: 2
    3
 0: 3
    4
 0: 4
    5
 0: 5
    6
 0: 6
    7
 0: 7
    8
 0: 8
    9
 0: 9
    10
 0: 10
    100
 0: 100
\= Expect no match
    abc
No match

/^.*nter/
    enter
 0: enter
    inter
 0: inter
    uponter
 0: uponter

/^xxx[0-9]+$/
    xxx0
 0: xxx0
    xxx1234
 0: xxx1234
\= Expect no match
    xxx
No match

/^.+[0-9][0-9][0-9]$/
    x123
 0: x123
    x1234
 0: x1234
    xx123
 0: xx123
    123456
 0: 123456
\= Expect no match
    123
No match

/^.+?[0-9][0-9][0-9]$/
    x123
 0: x123
    x1234
 0: x1234
    xx123
 0: xx123
    123456
 0: 123456
\= Expect no match
    123
No match

/^([^!]+)!(.+)=apquxz\.ixr\.zzz\.ac\.uk$/
    abc!pqr=apquxz.ixr.zzz.ac.uk
 0: abc!pqr=apquxz.ixr.zzz.ac.uk
 1: abc
 2: pqr
\= Expect no match
    !pqr=apquxz.ixr.zzz.ac.uk
No match
    abc!=apquxz.ixr.zzz.ac.uk
No match
    abc!pqr=apquxz:ixr.zzz.ac.uk
No match
    abc!pqr=apquxz.ixr.zzz.ac.ukk
No match

/:/
    Well, we need a colon: somewhere
 0: :
\= Expect no match
    Fail without a colon
No match

/([\da-f:]+)$/i
    0abc
 0: 0abc
 1: 0abc
    abc
 0: abc
 1: abc
    fed
 0: fed
 1: fed
    E
 0: E
 1: E
    ::
 0: ::
 1: ::
    5f03:12C0::932e
 0: 5f03:12C0::932e
 1: 5f03:12C0::932e
    fed def
 0: def
 1: def
    Any old stuff
 0: ff
 1: ff
\= Expect no match
    0zzz
No match
    gzzz
No match
    fed\x20
No match
    Any old rubbish
No match

/^.*\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})$/
    .1.2.3
 0: .1.2.3
 1: 1
 2: 2
 3: 3
    A.12.123.0
 0: A.12.123.0
 1: 12
 2: 123
 3: 0
\= Expect no match
    .1.2.3333
No match
    1.2.3
No match
    1234.2.3
No match

/^(\d+)\s+IN\s+SOA\s+(\S+)\s+(\S+)\s*\(\s*$/
    1 IN SOA non-sp1 non-sp2(
 0: 1 IN SOA non-sp1 non-sp2(
 1: 1
 2: non-sp1
 3: non-sp2
    1    IN    SOA    non-sp1    non-sp2   (
 0: 1    IN    SOA    non-sp1    non-sp2   (
 1: 1
 2: non-sp1
 3: non-sp2
\= Expect no match
    1IN SOA non-sp1 non-sp2(
No match

/^[a-zA-Z\d][a-zA-Z\d\-]*(\.[a-zA-Z\d][a-zA-z\d\-]*)*\.$/
    a.
 0: a.
    Z.
 0: Z.
    2.
 0: 2.
    ab-c.pq-r.
 0: ab-c.pq-r.
 1: .pq-r
    sxk.zzz.ac.uk.
 0: sxk.zzz.ac.uk.
 1: .uk
    x-.y-.
 0: x-.y-.
 1: .y-
\= Expect no match
    -abc.peq.
No match

/^\*\.[a-z]([a-z\-\d]*[a-z\d]+)?(\.[a-z]([a-z\-\d]*[a-z\d]+)?)*$/
    *.a
 0: *.a
    *.b0-a
 0: *.b0-a
 1: 0-a
    *.c3-b.c
 0: *.c3-b.c
 1: 3-b
 2: .c
    *.c-a.b-c
 0: *.c-a.b-c
 1: -a
 2: .b-c
 3: -c
\= Expect no match
    *.0
No match
    *.a-
No match
    *.a-b.c-
No match
    *.c-a.0-c
No match

/^(?=ab(de))(abd)(e)/
    abde
 0: abde
 1: de
 2: abd
 3: e

/^(?!(ab)de|x)(abd)(f)/
    abdf
 0: abdf
 1: <unset>
 2: abd
 3: f

/^(?=(ab(cd)))(ab)/
    abcd
 0: ab
 1: abcd
 2: cd
 3: ab

/^[\da-f](\.[\da-f])*$/i
    a.b.c.d
 0: a.b.c.d
 1: .d
    A.B.C.D
 0: A.B.C.D
 1: .D
    a.b.c.1.2.3.C
 0: a.b.c.1.2.3.C
 1: .C

/^\".*\"\s*(;.*)?$/
    \"1234\"
 0: "1234"
    \"abcd\" ;
 0: "abcd" ;
 1: ;
    \"\" ; rhubarb
 0: "" ; rhubarb
 1: ; rhubarb
\= Expect no match
    \"1234\" : things
No match

/^$/
    \
 0: 
\= Expect no match
    A non-empty line
No match

/   ^    a   (?# begins with a)  b\sc (?# then b c) $ (?# then end)/x
    ab c
 0: ab c
\= Expect no match
    abc
No match
    ab cde
No match

/(?x)   ^    a   (?# begins with a)  b\sc (?# then b c) $ (?# then end)/
    ab c
 0: ab c
\= Expect no match
    abc
No match
    ab cde
No match

/^   a\ b[c ]d       $/x
    a bcd
 0: a bcd
    a b d
 0: a b d
\= Expect no match
    abcd
No match
    ab d
No match

/^(a(b(c)))(d(e(f)))(h(i(j)))(k(l(m)))$/
    abcdefhijklm
 0: abcdefhijklm
 1: abc
 2: bc
 3: c
 4: def
 5: ef
 6: f
 7: hij
 8: ij
 9: j
10: klm
11: lm
12: m

/^(?:a(b(c)))(?:d(e(f)))(?:h(i(j)))(?:k(l(m)))$/
    abcdefhijklm
 0: abcdefhijklm
 1: bc
 2: c
 3: ef
 4: f
 5: ij
 6: j
 7: lm
 8: m

/^[\w][\W][\s][\S][\d][\D][\b][\n][\c]][\022]/
    a+ Z0+\x08\n\x1d\x12
 0: a+ Z0+\x08\x0a\x1d\x12

/^[.^$|()*+?{,}]+/
    .^\$(*+)|{?,?}
 0: .^$(*+)|{?,?}

/^a*\w/
    z
 0: z
    az
 0: az
    aaaz
 0: aaaz
    a
 0: a
    aa
 0: aa
    aaaa
 0: aaaa
    a+
 0: a
    aa+
 0: aa

/^a*?\w/
    z
 0: z
    az
 0: a
    aaaz
 0: a
    a
 0: a
    aa
 0: a
    aaaa
 0: a
    a+
 0: a
    aa+
 0: a

/^a+\w/
    az
 0: az
    aaaz
 0: aaaz
    aa
 0: aa
    aaaa
 0: aaaa
    aa+
 0: aa

/^a+?\w/
    az
 0: az
    aaaz
 0: aa
    aa
 0: aa
    aaaa
 0: aa
    aa+
 0: aa

/^\d{8}\w{2,}/
    1234567890
 0: 1234567890
    12345678ab
 0: 12345678ab
    12345678__
 0: 12345678__
\= Expect no match
    1234567
No match

/^[aeiou\d]{4,5}$/
    uoie
 0: uoie
    1234
 0: 1234
    12345
 0: 12345
    aaaaa
 0: aaaaa
\= Expect no match
    123456
No match

/^[aeiou\d]{4,5}?/
    uoie
 0: uoie
    1234
 0: 1234
    12345
 0: 1234
    aaaaa
 0: aaaa
    123456
 0: 1234

/\A(abc|def)=(\1){2,3}\Z/
    abc=abcabc
 0: abc=abcabc
 1: abc
 2: abc
    def=defdefdef
 0: def=defdefdef
 1: def
 2: def
\= Expect no match
    abc=defdef
No match

/^(a)(b)(c)(d)(e)(f)(g)(h)(i)(j)(k)\11*(\3\4)\1(?#)2$/
    abcdefghijkcda2
 0: abcdefghijkcda2
 1: a
 2: b
 3: c
 4: d
 5: e
 6: f
 7: g
 8: h
 9: i
10: j
11: k
12: cd
    abcdefghijkkkkcda2
 0: abcdefghijkkkkcda2
 1: a
 2: b
 3: c
 4: d
 5: e
 6: f
 7: g
 8: h
 9: i
10: j
11: k
12: cd

/(cat(a(ract|tonic)|erpillar)) \1()2(3)/
    cataract cataract23
 0: cataract cataract23
 1: cataract
 2: aract
 3: ract
 4: 
 5: 3
    catatonic catatonic23
 0: catatonic catatonic23
 1: catatonic
 2: atonic
 3: tonic
 4: 
 5: 3
    caterpillar caterpillar23
 0: caterpillar caterpillar23
 1: caterpillar
 2: erpillar
 3: <unset>
 4: 
 5: 3


/^From +([^ ]+) +[a-zA-Z][a-zA-Z][a-zA-Z] +[a-zA-Z][a-zA-Z][a-zA-Z] +[0-9]?[0-9] +[0-9][0-9]:[0-9][0-9]/
    From abcd  Mon Sep 01 12:33:02 1997
 0: From abcd  Mon Sep 01 12:33
 1: abcd

/^From\s+\S+\s+([a-zA-Z]{3}\s+){2}\d{1,2}\s+\d\d:\d\d/
    From abcd  Mon Sep 01 12:33:02 1997
 0: From abcd  Mon Sep 01 12:33
 1: Sep 
    From abcd  Mon Sep  1 12:33:02 1997
 0: From abcd  Mon Sep  1 12:33
 1: Sep  
\= Expect no match
    From abcd  Sep 01 12:33:02 1997
No match

/^12.34/s
    12\n34
 0: 12\x0a34
    12\r34
 0: 12\x0d34

/\w+(?=\t)/
    the quick brown\t fox
 0: brown

/foo(?!bar)(.*)/
    foobar is foolish see?
 0: foolish see?
 1: lish see?

/(?:(?!foo)...|^.{0,2})bar(.*)/
    foobar crowbar etc
 0: rowbar etc
 1:  etc
    barrel
 0: barrel
 1: rel
    2barrel
 0: 2barrel
 1: rel
    A barrel
 0: A barrel
 1: rel

/^(\D*)(?=\d)(?!123)/
    abc456
 0: abc
 1: abc
\= Expect no match
    abc123
No match

/^1234(?# test newlines
  inside)/
    1234
 0: 1234

/^1234 #comment in extended re
  /x
    1234
 0: 1234

/#rhubarb
  abcd/x
    abcd
 0: abcd

/^abcd#rhubarb/x
    abcd
 0: abcd

/^(a)\1{2,3}(.)/
    aaab
 0: aaab
 1: a
 2: b
    aaaab
 0: aaaab
 1: a
 2: b
    aaaaab
 0: aaaaa
 1: a
 2: a
    aaaaaab
 0: aaaaa
 1: a
 2: a

/(?!^)abc/
    the abc
 0: abc
\= Expect no match
    abc
No match

/(?=^)abc/
    abc
 0: abc
\= Expect no match
    the abc
No match

/^[ab]{1,3}(ab*|b)/
    aabbbbb
 0: aabb
 1: b

/^[ab]{1,3}?(ab*|b)/
    aabbbbb
 0: aabbbbb
 1: abbbbb

/^[ab]{1,3}?(ab*?|b)/
    aabbbbb
 0: aa
 1: a

/^[ab]{1,3}(ab*?|b)/
    aabbbbb
 0: aabb
 1: b

/  (?: [\040\t] |  \(
(?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  |  \( (?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  )* \)  )*
\)  )*                          # optional leading comment
(?:    (?:
[^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]+    # some number of atom characters...
(?![^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]) # ..not followed by something that could be part of an atom
|
" (?:                      # opening quote...
[^\\\x80-\xff\n\015"]                #   Anything except backslash and quote
|                     #    or
\\ [^\x80-\xff]           #   Escaped something (something != CR)
)* "  # closing quote
)                    # initial word
(?:  (?: [\040\t] |  \(
(?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  |  \( (?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  )* \)  )*
\)  )*  \.  (?: [\040\t] |  \(
(?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  |  \( (?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  )* \)  )*
\)  )*   (?:
[^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]+    # some number of atom characters...
(?![^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]) # ..not followed by something that could be part of an atom
|
" (?:                      # opening quote...
[^\\\x80-\xff\n\015"]                #   Anything except backslash and quote
|                     #    or
\\ [^\x80-\xff]           #   Escaped something (something != CR)
)* "  # closing quote
)  )* # further okay, if led by a period
(?: [\040\t] |  \(
(?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  |  \( (?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  )* \)  )*
\)  )*  @  (?: [\040\t] |  \(
(?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  |  \( (?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  )* \)  )*
\)  )*    (?:
[^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]+    # some number of atom characters...
(?![^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]) # ..not followed by something that could be part of an atom
|   \[                         # [
(?: [^\\\x80-\xff\n\015\[\]] |  \\ [^\x80-\xff]  )*    #    stuff
\]                        #           ]
)                           # initial subdomain
(?:                                  #
(?: [\040\t] |  \(
(?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  |  \( (?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  )* \)  )*
\)  )*  \.                        # if led by a period...
(?: [\040\t] |  \(
(?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  |  \( (?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  )* \)  )*
\)  )*   (?:
[^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]+    # some number of atom characters...
(?![^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]) # ..not followed by something that could be part of an atom
|   \[                         # [
(?: [^\\\x80-\xff\n\015\[\]] |  \\ [^\x80-\xff]  )*    #    stuff
\]                        #           ]
)                     #   ...further okay
)*
# address
|                     #  or
(?:
[^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]+    # some number of atom characters...
(?![^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]) # ..not followed by something that could be part of an atom
|
" (?:                      # opening quote...
[^\\\x80-\xff\n\015"]                #   Anything except backslash and quote
|                     #    or
\\ [^\x80-\xff]           #   Escaped something (something != CR)
)* "  # closing quote
)             # one word, optionally followed by....
(?:
[^()<>@,;:".\\\[\]\x80-\xff\000-\010\012-\037]  |  # atom and space parts, or...
\(
(?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  |  \( (?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  )* \)  )*
\)       |  # comments, or...

" (?:                      # opening quote...
[^\\\x80-\xff\n\015"]                #   Anything except backslash and quote
|                     #    or
\\ [^\x80-\xff]           #   Escaped something (something != CR)
)* "  # closing quote
# quoted strings
)*
<  (?: [\040\t] |  \(
(?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  |  \( (?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  )* \)  )*
\)  )*                     # leading <
(?:  @  (?: [\040\t] |  \(
(?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  |  \( (?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  )* \)  )*
\)  )*    (?:
[^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]+    # some number of atom characters...
(?![^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]) # ..not followed by something that could be part of an atom
|   \[                         # [
(?: [^\\\x80-\xff\n\015\[\]] |  \\ [^\x80-\xff]  )*    #    stuff
\]                        #           ]
)                           # initial subdomain
(?:                                  #
(?: [\040\t] |  \(
(?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  |  \( (?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  )* \)  )*
\)  )*  \.                        # if led by a period...
(?: [\040\t] |  \(
(?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  |  \( (?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  )* \)  )*
\)  )*   (?:
[^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]+    # some number of atom characters...
(?![^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]) # ..not followed by something that could be part of an atom
|   \[                         # [
(?: [^\\\x80-\xff\n\015\[\]] |  \\ [^\x80-\xff]  )*    #    stuff
\]                        #           ]
)                     #   ...further okay
)*

(?:  (?: [\040\t] |  \(
(?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  |  \( (?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  )* \)  )*
\)  )*  ,  (?: [\040\t] |  \(
(?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  |  \( (?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  )* \)  )*
\)  )*  @  (?: [\040\t] |  \(
(?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  |  \( (?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  )* \)  )*
\)  )*    (?:
[^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]+    # some number of atom characters...
(?![^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]) # ..not followed by something that could be part of an atom
|   \[                         # [
(?: [^\\\x80-\xff\n\015\[\]] |  \\ [^\x80-\xff]  )*    #    stuff
\]                        #           ]
)                           # initial subdomain
(?:                                  #
(?: [\040\t] |  \(
(?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  |  \( (?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  )* \)  )*
\)  )*  \.                        # if led by a period...
(?: [\040\t] |  \(
(?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  |  \( (?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  )* \)  )*
\)  )*   (?:
[^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]+    # some number of atom characters...
(?![^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]) # ..not followed by something that could be part of an atom
|   \[                         # [
(?: [^\\\x80-\xff\n\015\[\]] |  \\ [^\x80-\xff]  )*    #    stuff
\]                        #           ]
)                     #   ...further okay
)*
)* # further okay, if led by comma
:                                # closing colon
(?: [\040\t] |  \(
(?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  |  \( (?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  )* \)  )*
\)  )*  )? #       optional route
(?:
[^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]+    # some number of atom characters...
(?![^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]) # ..not followed by something that could be part of an atom
|
" (?:                      # opening quote...
[^\\\x80-\xff\n\015"]                #   Anything except backslash and quote
|                     #    or
\\ [^\x80-\xff]           #   Escaped something (something != CR)
)* "  # closing quote
)                    # initial word
(?:  (?: [\040\t] |  \(
(?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  |  \( (?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  )* \)  )*
\)  )*  \.  (?: [\040\t] |  \(
(?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  |  \( (?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  )* \)  )*
\)  )*   (?:
[^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]+    # some number of atom characters...
(?![^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]) # ..not followed by something that could be part of an atom
|
" (?:                      # opening quote...
[^\\\x80-\xff\n\015"]                #   Anything except backslash and quote
|                     #    or
\\ [^\x80-\xff]           #   Escaped something (something != CR)
)* "  # closing quote
)  )* # further okay, if led by a period
(?: [\040\t] |  \(
(?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  |  \( (?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  )* \)  )*
\)  )*  @  (?: [\040\t] |  \(
(?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  |  \( (?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  )* \)  )*
\)  )*    (?:
[^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]+    # some number of atom characters...
(?![^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]) # ..not followed by something that could be part of an atom
|   \[                         # [
(?: [^\\\x80-\xff\n\015\[\]] |  \\ [^\x80-\xff]  )*    #    stuff
\]                        #           ]
)                           # initial subdomain
(?:                                  #
(?: [\040\t] |  \(
(?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  |  \( (?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  )* \)  )*
\)  )*  \.                        # if led by a period...
(?: [\040\t] |  \(
(?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  |  \( (?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  )* \)  )*
\)  )*   (?:
[^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]+    # some number of atom characters...
(?![^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]) # ..not followed by something that could be part of an atom
|   \[                         # [
(?: [^\\\x80-\xff\n\015\[\]] |  \\ [^\x80-\xff]  )*    #    stuff
\]                        #           ]
)                     #   ...further okay
)*
#       address spec
(?: [\040\t] |  \(
(?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  |  \( (?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  )* \)  )*
\)  )*  > #                  trailing >
# name and address
)  (?: [\040\t] |  \(
(?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  |  \( (?:  [^\\\x80-\xff\n\015()]  |  \\ [^\x80-\xff]  )* \)  )*
\)  )*                       # optional trailing comment
/x
    Alan Other <user\@dom.ain>
 0: Alan Other <user@dom.ain>
    <user\@dom.ain>
 0: user@dom.ain
    user\@dom.ain
 0: user@dom.ain
    \"A. Other\" <user.1234\@dom.ain> (a comment)
 0: "A. Other" <user.1234@dom.ain> (a comment)
    A. Other <user.1234\@dom.ain> (a comment)
 0:  Other <user.1234@dom.ain> (a comment)
    \"/s=user/ou=host/o=place/prmd=uu.yy/admd= /c=gb/\"\@x400-re.lay
 0: "/s=user/ou=host/o=place/prmd=uu.yy/admd= /c=gb/"@x400-re.lay
    A missing angle <user\@some.where
 0: user@some.where
\= Expect no match
    The quick brown fox
No match

/[\040\t]*                    # Nab whitespace.
(?:
\(                              #  (
[^\\\x80-\xff\n\015()] *                             #     normal*
(?:                                 #       (
(?:  \\ [^\x80-\xff]  |
\(                            #  (
[^\\\x80-\xff\n\015()] *                            #     normal*
(?:  \\ [^\x80-\xff]   [^\\\x80-\xff\n\015()] * )*        #     (special normal*)*
\)                           #                       )
)    #         special
[^\\\x80-\xff\n\015()] *                         #         normal*
)*                                  #            )*
\)                             #                )
[\040\t]* )*    # If comment found, allow more spaces.
# optional leading comment
(?:
(?:
[^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]+    # some number of atom characters...
(?![^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]) # ..not followed by something that could be part of an atom
# Atom
|                       #  or
"                                     # "
[^\\\x80-\xff\n\015"] *                            #   normal
(?:  \\ [^\x80-\xff]  [^\\\x80-\xff\n\015"] * )*        #   ( special normal* )*
"                                     #        "
# Quoted string
)
[\040\t]*                    # Nab whitespace.
(?:
\(                              #  (
[^\\\x80-\xff\n\015()] *                             #     normal*
(?:                                 #       (
(?:  \\ [^\x80-\xff]  |
\(                            #  (
[^\\\x80-\xff\n\015()] *                            #     normal*
(?:  \\ [^\x80-\xff]   [^\\\x80-\xff\n\015()] * )*        #     (special normal*)*
\)                           #                       )
)    #         special
[^\\\x80-\xff\n\015()] *                         #         normal*
)*                                  #            )*
\)                             #                )
[\040\t]* )*    # If comment found, allow more spaces.
(?:
\.
[\040\t]*                    # Nab whitespace.
(?:
\(                              #  (
[^\\\x80-\xff\n\015()] *                             #     normal*
(?:                                 #       (
(?:  \\ [^\x80-\xff]  |
\(                            #  (
[^\\\x80-\xff\n\015()] *                            #     normal*
(?:  \\ [^\x80-\xff]   [^\\\x80-\xff\n\015()] * )*        #     (special normal*)*
\)                           #                       )
)    #         special
[^\\\x80-\xff\n\015()] *                         #         normal*
)*                                  #            )*
\)                             #                )
[\040\t]* )*    # If comment found, allow more spaces.
(?:
[^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]+    # some number of atom characters...
(?![^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]) # ..not followed by something that could be part of an atom
# Atom
|                       #  or
"                                     # "
[^\\\x80-\xff\n\015"] *                            #   normal
(?:  \\ [^\x80-\xff]  [^\\\x80-\xff\n\015"] * )*        #   ( special normal* )*
"                                     #        "
# Quoted string
)
[\040\t]*                    # Nab whitespace.
(?:
\(                              #  (
[^\\\x80-\xff\n\015()] *                             #     normal*
(?:                                 #       (
(?:  \\ [^\x80-\xff]  |
\(                            #  (
[^\\\x80-\xff\n\015()] *                            #     normal*
(?:  \\ [^\x80-\xff]   [^\\\x80-\xff\n\015()] * )*        #     (special normal*)*
\)                           #                       )
)    #         special
[^\\\x80-\xff\n\015()] *                         #         normal*
)*                                  #            )*
\)                             #                )
[\040\t]* )*    # If comment found, allow more spaces.
# additional words
)*
@
[\040\t]*                    # Nab whitespace.
(?:
\(                              #  (
[^\\\x80-\xff\n\015()] *                             #     normal*
(?:                                 #       (
(?:  \\ [^\x80-\xff]  |
\(                            #  (
[^\\\x80-\xff\n\015()] *                            #     normal*
(?:  \\ [^\x80-\xff]   [^\\\x80-\xff\n\015()] * )*        #     (special normal*)*
\)                           #                       )
)    #         special
[^\\\x80-\xff\n\015()] *                         #         normal*
)*                                  #            )*
\)                             #                )
[\040\t]* )*    # If comment found, allow more spaces.
(?:
[^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]+    # some number of atom characters...
(?![^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]) # ..not followed by something that could be part of an atom
|
\[                            # [
(?: [^\\\x80-\xff\n\015\[\]] |  \\ [^\x80-\xff]  )*     #    stuff
\]                           #           ]
)
[\040\t]*                    # Nab whitespace.
(?:
\(                              #  (
[^\\\x80-\xff\n\015()] *                             #     normal*
(?:                                 #       (
(?:  \\ [^\x80-\xff]  |
\(                            #  (
[^\\\x80-\xff\n\015()] *                            #     normal*
(?:  \\ [^\x80-\xff]   [^\\\x80-\xff\n\015()] * )*        #     (special normal*)*
\)                           #                       )
)    #         special
[^\\\x80-\xff\n\015()] *                         #         normal*
)*                                  #            )*
\)                             #                )
[\040\t]* )*    # If comment found, allow more spaces.
# optional trailing comments
(?:
\.
[\040\t]*                    # Nab whitespace.
(?:
\(                              #  (
[^\\\x80-\xff\n\015()] *                             #     normal*
(?:                                 #       (
(?:  \\ [^\x80-\xff]  |
\(                            #  (
[^\\\x80-\xff\n\015()] *                            #     normal*
(?:  \\ [^\x80-\xff]   [^\\\x80-\xff\n\015()] * )*        #     (special normal*)*
\)                           #                       )
)    #         special
[^\\\x80-\xff\n\015()] *                         #         normal*
)*                                  #            )*
\)                             #                )
[\040\t]* )*    # If comment found, allow more spaces.
(?:
[^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]+    # some number of atom characters...
(?![^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]) # ..not followed by something that could be part of an atom
|
\[                            # [
(?: [^\\\x80-\xff\n\015\[\]] |  \\ [^\x80-\xff]  )*     #    stuff
\]                           #           ]
)
[\040\t]*                    # Nab whitespace.
(?:
\(                              #  (
[^\\\x80-\xff\n\015()] *                             #     normal*
(?:                                 #       (
(?:  \\ [^\x80-\xff]  |
\(                            #  (
[^\\\x80-\xff\n\015()] *                            #     normal*
(?:  \\ [^\x80-\xff]   [^\\\x80-\xff\n\015()] * )*        #     (special normal*)*
\)                           #                       )
)    #         special
[^\\\x80-\xff\n\015()] *                         #         normal*
)*                                  #            )*
\)                             #                )
[\040\t]* )*    # If comment found, allow more spaces.
# optional trailing comments
)*
# address
|                             #  or
(?:
[^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]+    # some number of atom characters...
(?![^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]) # ..not followed by something that could be part of an atom
# Atom
|                       #  or
"                                     # "
[^\\\x80-\xff\n\015"] *                            #   normal
(?:  \\ [^\x80-\xff]  [^\\\x80-\xff\n\015"] * )*        #   ( special normal* )*
"                                     #        "
# Quoted string
)
# leading word
[^()<>@,;:".\\\[\]\x80-\xff\000-\010\012-\037] *               # "normal" atoms and or spaces
(?:
(?:
\(                              #  (
[^\\\x80-\xff\n\015()] *                             #     normal*
(?:                                 #       (
(?:  \\ [^\x80-\xff]  |
\(                            #  (
[^\\\x80-\xff\n\015()] *                            #     normal*
(?:  \\ [^\x80-\xff]   [^\\\x80-\xff\n\015()] * )*        #     (special normal*)*
\)                           #                       )
)    #         special
[^\\\x80-\xff\n\015()] *                         #         normal*
)*                                  #            )*
\)                             #                )
|
"                                     # "
[^\\\x80-\xff\n\015"] *                            #   normal
(?:  \\ [^\x80-\xff]  [^\\\x80-\xff\n\015"] * )*        #   ( special normal* )*
"                                     #        "
) # "special" comment or quoted string
[^()<>@,;:".\\\[\]\x80-\xff\000-\010\012-\037] *            #  more "normal"
)*
<
[\040\t]*                    # Nab whitespace.
(?:
\(                              #  (
[^\\\x80-\xff\n\015()] *                             #     normal*
(?:                                 #       (
(?:  \\ [^\x80-\xff]  |
\(                            #  (
[^\\\x80-\xff\n\015()] *                            #     normal*
(?:  \\ [^\x80-\xff]   [^\\\x80-\xff\n\015()] * )*        #     (special normal*)*
\)                           #                       )
)    #         special
[^\\\x80-\xff\n\015()] *                         #         normal*
)*                                  #            )*
\)                             #                )
[\040\t]* )*    # If comment found, allow more spaces.
# <
(?:
@
[\040\t]*                    # Nab whitespace.
(?:
\(                              #  (
[^\\\x80-\xff\n\015()] *                             #     normal*
(?:                                 #       (
(?:  \\ [^\x80-\xff]  |
\(                            #  (
[^\\\x80-\xff\n\015()] *                            #     normal*
(?:  \\ [^\x80-\xff]   [^\\\x80-\xff\n\015()] * )*        #     (special normal*)*
\)                           #                       )
)    #         special
[^\\\x80-\xff\n\015()] *                         #         normal*
)*                                  #            )*
\)                             #                )
[\040\t]* )*    # If comment found, allow more spaces.
(?:
[^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]+    # some number of atom characters...
(?![^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]) # ..not followed by something that could be part of an atom
|
\[                            # [
(?: [^\\\x80-\xff\n\015\[\]] |  \\ [^\x80-\xff]  )*     #    stuff
\]                           #           ]
)
[\040\t]*                    # Nab whitespace.
(?:
\(                              #  (
[^\\\x80-\xff\n\015()] *                             #     normal*
(?:                                 #       (
(?:  \\ [^\x80-\xff]  |
\(                            #  (
[^\\\x80-\xff\n\015()] *                            #     normal*
(?:  \\ [^\x80-\xff]   [^\\\x80-\xff\n\015()] * )*        #     (special normal*)*
\)                           #                       )
)    #         special
[^\\\x80-\xff\n\015()] *                         #         normal*
)*                                  #            )*
\)                             #                )
[\040\t]* )*    # If comment found, allow more spaces.
# optional trailing comments
(?:
\.
[\040\t]*                    # Nab whitespace.
(?:
\(                              #  (
[^\\\x80-\xff\n\015()] *                             #     normal*
(?:                                 #       (
(?:  \\ [^\x80-\xff]  |
\(                            #  (
[^\\\x80-\xff\n\015()] *                            #     normal*
(?:  \\ [^\x80-\xff]   [^\\\x80-\xff\n\015()] * )*        #     (special normal*)*
\)                           #                       )
)    #         special
[^\\\x80-\xff\n\015()] *                         #         normal*
)*                                  #            )*
\)                             #                )
[\040\t]* )*    # If comment found, allow more spaces.
(?:
[^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]+    # some number of atom characters...
(?![^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]) # ..not followed by something that could be part of an atom
|
\[                            # [
(?: [^\\\x80-\xff\n\015\[\]] |  \\ [^\x80-\xff]  )*     #    stuff
\]                           #           ]
)
[\040\t]*                    # Nab whitespace.
(?:
\(                              #  (
[^\\\x80-\xff\n\015()] *                             #     normal*
(?:                                 #       (
(?:  \\ [^\x80-\xff]  |
\(                            #  (
[^\\\x80-\xff\n\015()] *                            #     normal*
(?:  \\ [^\x80-\xff]   [^\\\x80-\xff\n\015()] * )*        #     (special normal*)*
\)                           #                       )
)    #         special
[^\\\x80-\xff\n\015()] *                         #         normal*
)*                                  #            )*
\)                             #                )
[\040\t]* )*    # If comment found, allow more spaces.
# optional trailing comments
)*
(?: ,
[\040\t]*                    # Nab whitespace.
(?:
\(                              #  (
[^\\\x80-\xff\n\015()] *                             #     normal*
(?:                                 #       (
(?:  \\ [^\x80-\xff]  |
\(                            #  (
[^\\\x80-\xff\n\015()] *                            #     normal*
(?:  \\ [^\x80-\xff]   [^\\\x80-\xff\n\015()] * )*        #     (special normal*)*
\)                           #                       )
)    #         special
[^\\\x80-\xff\n\015()] *                         #         normal*
)*                                  #            )*
\)                             #                )
[\040\t]* )*    # If comment found, allow more spaces.
@
[\040\t]*                    # Nab whitespace.
(?:
\(                              #  (
[^\\\x80-\xff\n\015()] *                             #     normal*
(?:                                 #       (
(?:  \\ [^\x80-\xff]  |
\(                            #  (
[^\\\x80-\xff\n\015()] *                            #     normal*
(?:  \\ [^\x80-\xff]   [^\\\x80-\xff\n\015()] * )*        #     (special normal*)*
\)                           #                       )
)    #         special
[^\\\x80-\xff\n\015()] *                         #         normal*
)*                                  #            )*
\)                             #                )
[\040\t]* )*    # If comment found, allow more spaces.
(?:
[^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]+    # some number of atom characters...
(?![^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]) # ..not followed by something that could be part of an atom
|
\[                            # [
(?: [^\\\x80-\xff\n\015\[\]] |  \\ [^\x80-\xff]  )*     #    stuff
\]                           #           ]
)
[\040\t]*                    # Nab whitespace.
(?:
\(                              #  (
[^\\\x80-\xff\n\015()] *                             #     normal*
(?:                                 #       (
(?:  \\ [^\x80-\xff]  |
\(                            #  (
[^\\\x80-\xff\n\015()] *                            #     normal*
(?:  \\ [^\x80-\xff]   [^\\\x80-\xff\n\015()] * )*        #     (special normal*)*
\)                           #                       )
)    #         special
[^\\\x80-\xff\n\015()] *                         #         normal*
)*                                  #            )*
\)                             #                )
[\040\t]* )*    # If comment found, allow more spaces.
# optional trailing comments
(?:
\.
[\040\t]*                    # Nab whitespace.
(?:
\(                              #  (
[^\\\x80-\xff\n\015()] *                             #     normal*
(?:                                 #       (
(?:  \\ [^\x80-\xff]  |
\(                            #  (
[^\\\x80-\xff\n\015()] *                            #     normal*
(?:  \\ [^\x80-\xff]   [^\\\x80-\xff\n\015()] * )*        #     (special normal*)*
\)                           #                       )
)    #         special
[^\\\x80-\xff\n\015()] *                         #         normal*
)*                                  #            )*
\)                             #                )
[\040\t]* )*    # If comment found, allow more spaces.
(?:
[^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]+    # some number of atom characters...
(?![^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]) # ..not followed by something that could be part of an atom
|
\[                            # [
(?: [^\\\x80-\xff\n\015\[\]] |  \\ [^\x80-\xff]  )*     #    stuff
\]                           #           ]
)
[\040\t]*                    # Nab whitespace.
(?:
\(                              #  (
[^\\\x80-\xff\n\015()] *                             #     normal*
(?:                                 #       (
(?:  \\ [^\x80-\xff]  |
\(                            #  (
[^\\\x80-\xff\n\015()] *                            #     normal*
(?:  \\ [^\x80-\xff]   [^\\\x80-\xff\n\015()] * )*        #     (special normal*)*
\)                           #                       )
)    #         special
[^\\\x80-\xff\n\015()] *                         #         normal*
)*                                  #            )*
\)                             #                )
[\040\t]* )*    # If comment found, allow more spaces.
# optional trailing comments
)*
)*  # additional domains
:
[\040\t]*                    # Nab whitespace.
(?:
\(                              #  (
[^\\\x80-\xff\n\015()] *                             #     normal*
(?:                                 #       (
(?:  \\ [^\x80-\xff]  |
\(                            #  (
[^\\\x80-\xff\n\015()] *                            #     normal*
(?:  \\ [^\x80-\xff]   [^\\\x80-\xff\n\015()] * )*        #     (special normal*)*
\)                           #                       )
)    #         special
[^\\\x80-\xff\n\015()] *                         #         normal*
)*                                  #            )*
\)                             #                )
[\040\t]* )*    # If comment found, allow more spaces.
# optional trailing comments
)?     #       optional route
(?:
[^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]+    # some number of atom characters...
(?![^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]) # ..not followed by something that could be part of an atom
# Atom
|                       #  or
"                                     # "
[^\\\x80-\xff\n\015"] *                            #   normal
(?:  \\ [^\x80-\xff]  [^\\\x80-\xff\n\015"] * )*        #   ( special normal* )*
"                                     #        "
# Quoted string
)
[\040\t]*                    # Nab whitespace.
(?:
\(                              #  (
[^\\\x80-\xff\n\015()] *                             #     normal*
(?:                                 #       (
(?:  \\ [^\x80-\xff]  |
\(                            #  (
[^\\\x80-\xff\n\015()] *                            #     normal*
(?:  \\ [^\x80-\xff]   [^\\\x80-\xff\n\015()] * )*        #     (special normal*)*
\)                           #                       )
)    #         special
[^\\\x80-\xff\n\015()] *                         #         normal*
)*                                  #            )*
\)                             #                )
[\040\t]* )*    # If comment found, allow more spaces.
(?:
\.
[\040\t]*                    # Nab whitespace.
(?:
\(                              #  (
[^\\\x80-\xff\n\015()] *                             #     normal*
(?:                                 #       (
(?:  \\ [^\x80-\xff]  |
\(                            #  (
[^\\\x80-\xff\n\015()] *                            #     normal*
(?:  \\ [^\x80-\xff]   [^\\\x80-\xff\n\015()] * )*        #     (special normal*)*
\)                           #                       )
)    #         special
[^\\\x80-\xff\n\015()] *                         #         normal*
)*                                  #            )*
\)                             #                )
[\040\t]* )*    # If comment found, allow more spaces.
(?:
[^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]+    # some number of atom characters...
(?![^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]) # ..not followed by something that could be part of an atom
# Atom
|                       #  or
"                                     # "
[^\\\x80-\xff\n\015"] *                            #   normal
(?:  \\ [^\x80-\xff]  [^\\\x80-\xff\n\015"] * )*        #   ( special normal* )*
"                                     #        "
# Quoted string
)
[\040\t]*                    # Nab whitespace.
(?:
\(                              #  (
[^\\\x80-\xff\n\015()] *                             #     normal*
(?:                                 #       (
(?:  \\ [^\x80-\xff]  |
\(                            #  (
[^\\\x80-\xff\n\015()] *                            #     normal*
(?:  \\ [^\x80-\xff]   [^\\\x80-\xff\n\015()] * )*        #     (special normal*)*
\)                           #                       )
)    #         special
[^\\\x80-\xff\n\015()] *                         #         normal*
)*                                  #            )*
\)                             #                )
[\040\t]* )*    # If comment found, allow more spaces.
# additional words
)*
@
[\040\t]*                    # Nab whitespace.
(?:
\(                              #  (
[^\\\x80-\xff\n\015()] *                             #     normal*
(?:                                 #       (
(?:  \\ [^\x80-\xff]  |
\(                            #  (
[^\\\x80-\xff\n\015()] *                            #     normal*
(?:  \\ [^\x80-\xff]   [^\\\x80-\xff\n\015()] * )*        #     (special normal*)*
\)                           #                       )
)    #         special
[^\\\x80-\xff\n\015()] *                         #         normal*
)*                                  #            )*
\)                             #                )
[\040\t]* )*    # If comment found, allow more spaces.
(?:
[^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]+    # some number of atom characters...
(?![^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]) # ..not followed by something that could be part of an atom
|
\[                            # [
(?: [^\\\x80-\xff\n\015\[\]] |  \\ [^\x80-\xff]  )*     #    stuff
\]                           #           ]
)
[\040\t]*                    # Nab whitespace.
(?:
\(                              #  (
[^\\\x80-\xff\n\015()] *                             #     normal*
(?:                                 #       (
(?:  \\ [^\x80-\xff]  |
\(                            #  (
[^\\\x80-\xff\n\015()] *                            #     normal*
(?:  \\ [^\x80-\xff]   [^\\\x80-\xff\n\015()] * )*        #     (special normal*)*
\)                           #                       )
)    #         special
[^\\\x80-\xff\n\015()] *                         #         normal*
)*                                  #            )*
\)                             #                )
[\040\t]* )*    # If comment found, allow more spaces.
# optional trailing comments
(?:
\.
[\040\t]*                    # Nab whitespace.
(?:
\(                              #  (
[^\\\x80-\xff\n\015()] *                             #     normal*
(?:                                 #       (
(?:  \\ [^\x80-\xff]  |
\(                            #  (
[^\\\x80-\xff\n\015()] *                            #     normal*
(?:  \\ [^\x80-\xff]   [^\\\x80-\xff\n\015()] * )*        #     (special normal*)*
\)                           #                       )
)    #         special
[^\\\x80-\xff\n\015()] *                         #         normal*
)*                                  #            )*
\)                             #                )
[\040\t]* )*    # If comment found, allow more spaces.
(?:
[^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]+    # some number of atom characters...
(?![^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]) # ..not followed by something that could be part of an atom
|
\[                            # [
(?: [^\\\x80-\xff\n\015\[\]] |  \\ [^\x80-\xff]  )*     #    stuff
\]                           #           ]
)
[\040\t]*                    # Nab whitespace.
(?:
\(                              #  (
[^\\\x80-\xff\n\015()] *                             #     normal*
(?:                                 #       (
(?:  \\ [^\x80-\xff]  |
\(                            #  (
[^\\\x80-\xff\n\015()] *                            #     normal*
(?:  \\ [^\x80-\xff]   [^\\\x80-\xff\n\015()] * )*        #     (special normal*)*
\)                           #                       )
)    #         special
[^\\\x80-\xff\n\015()] *                         #         normal*
)*                                  #            )*
\)                             #                )
[\040\t]* )*    # If comment found, allow more spaces.
# optional trailing comments
)*
#       address spec
>                    #                 >
# name and address
)
/x
    Alan Other <user\@dom.ain>
 0: Alan Other <user@dom.ain>
    <user\@dom.ain>
 0: user@dom.ain
    user\@dom.ain
 0: user@dom.ain
    \"A. Other\" <user.1234\@dom.ain> (a comment)
 0: "A. Other" <user.1234@dom.ain>
    A. Other <user.1234\@dom.ain> (a comment)
 0:  Other <user.1234@dom.ain>
    \"/s=user/ou=host/o=place/prmd=uu.yy/admd= /c=gb/\"\@x400-re.lay
 0: "/s=user/ou=host/o=place/prmd=uu.yy/admd= /c=gb/"@x400-re.lay
    A missing angle <user\@some.where
 0: user@some.where
\= Expect no match
    The quick brown fox
No match

/abc\0def\00pqr\000xyz\0000AB/
    abc\0def\00pqr\000xyz\0000AB
 0: abc\x00def\x00pqr\x00xyz\x000AB
    abc456 abc\0def\00pqr\000xyz\0000ABCDE
 0: abc\x00def\x00pqr\x00xyz\x000AB

/abc\x0def\x00pqr\x000xyz\x0000AB/
    abc\x0def\x00pqr\x000xyz\x0000AB
 0: abc\x0def\x00pqr\x000xyz\x0000AB
    abc456 abc\x0def\x00pqr\x000xyz\x0000ABCDE
 0: abc\x0def\x00pqr\x000xyz\x0000AB

/^[\000-\037]/
    \0A
 0: \x00
    \01B
 0: \x01
    \037C
 0: \x1f

/\0*/
    \0\0\0\0
 0: \x00\x00\x00\x00

/A\x0{2,3}Z/
    The A\x0\x0Z
 0: A\x00\x00Z
    An A\0\x0\0Z
 0: A\x00\x00\x00Z
\= Expect no match
    A\0Z
No match
    A\0\x0\0\x0Z
No match

/^(cow|)\1(bell)/
    cowcowbell
 0: cowcowbell
 1: cow
 2: bell
    bell
 0: bell
 1: 
 2: bell
\= Expect no match
    cowbell
No match

/^\s/
    \040abc
 0:  
    \x0cabc
 0: \x0c
    \nabc
 0: \x0a
    \rabc
 0: \x0d
    \tabc
 0: \x09
\= Expect no match
    abc
No match

/^a	b
      c/x
    abc
 0: abc

/^(a|)\1*b/
    ab
 0: ab
 1: a
    aaaab
 0: aaaab
 1: a
    b
 0: b
 1: 
\= Expect no match
    acb
No match

/^(a|)\1+b/
    aab
 0: aab
 1: a
    aaaab
 0: aaaab
 1: a
    b
 0: b
 1: 
\= Expect no match
    ab
No match

/^(a|)\1?b/
    ab
 0: ab
 1: a
    aab
 0: aab
 1: a
    b
 0: b
 1: 
\= Expect no match
    acb
No match

/^(a|)\1{2}b/
    aaab
 0: aaab
 1: a
    b
 0: b
 1: 
\= Expect no match
    ab
No match
    aab
No match
    aaaab
No match

/^(a|)\1{2,3}b/
    aaab
 0: aaab
 1: a
    aaaab
 0: aaaab
 1: a
    b
 0: b
 1: 
\= Expect no match
    ab
No match
    aab
No match
    aaaaab
No match

/ab{1,3}bc/
    abbbbc
 0: abbbbc
    abbbc
 0: abbbc
    abbc
 0: abbc
\= Expect no match
    abc
No match
    abbbbbc
No match

/([^.]*)\.([^:]*):[T ]+(.*)/
    track1.title:TBlah blah blah
 0: track1.title:TBlah blah blah
 1: track1
 2: title
 3: Blah blah blah

/([^.]*)\.([^:]*):[T ]+(.*)/i
    track1.title:TBlah blah blah
 0: track1.title:TBlah blah blah
 1: track1
 2: title
 3: Blah blah blah

/([^.]*)\.([^:]*):[t ]+(.*)/i
    track1.title:TBlah blah blah
 0: track1.title:TBlah blah blah
 1: track1
 2: title
 3: Blah blah blah

/^[W-c]+$/
    WXY_^abc
 0: WXY_^abc
\= Expect no match
    wxy
No match

/^[W-c]+$/i
    WXY_^abc
 0: WXY_^abc
    wxy_^ABC
 0: wxy_^ABC

/^[\x3f-\x5F]+$/i
    WXY_^abc
 0: WXY_^abc
    wxy_^ABC
 0: wxy_^ABC

/^abc$/m
    abc
 0: abc
    qqq\nabc
 0: abc
    abc\nzzz
 0: abc
    qqq\nabc\nzzz
 0: abc

/^abc$/
    abc
 0: abc
\= Expect no match
    qqq\nabc
No match
    abc\nzzz
No match
    qqq\nabc\nzzz
No match

/\Aabc\Z/m
    abc
 0: abc
    abc\n 
 0: abc
\= Expect no match
    qqq\nabc
No match
    abc\nzzz
No match
    qqq\nabc\nzzz
No match
    
/\A(.)*\Z/s
    abc\ndef
 0: abc\x0adef
 1: f

/\A(.)*\Z/m
\= Expect no match
    abc\ndef
No match

/(?:b)|(?::+)/
    b::c
 0: b
    c::b
 0: ::

/[-az]+/
    az-
 0: az-
\= Expect no match
    b
No match

/[az-]+/
    za-
 0: za-
\= Expect no match
    b
No match

/[a\-z]+/
    a-z
 0: a-z
\= Expect no match
    b
No match

/[a-z]+/
    abcdxyz
 0: abcdxyz

/[\d-]+/
    12-34
 0: 12-34
\= Expect no match
    aaa
No match

/\x5c/
    \\
 0: \

/\x20Z/
    the Zoo
 0:  Z
\= Expect no match
    Zulu
No match

/(abc)\1/i
    abcabc
 0: abcabc
 1: abc
    ABCabc
 0: ABCabc
 1: ABC
    abcABC
 0: abcABC
 1: abc

/abc$/
    abc
 0: abc
    abc\n
 0: abc
\= Expect no match
    abc\ndef
No match

/(abc)\123/
    abc\x53
 0: abcS
 1: abc

/(abc)\223/
    abc\x93
 0: abc\x93
 1: abc

/(abc)\323/
    abc\xd3
 0: abc\xd3
 1: abc

/(abc)\100/
    abc\x40
 0: abc@
 1: abc
    abc\100
 0: abc@
 1: abc

/(abc)\1000/
    abc\x400
 0: abc@0
 1: abc
    abc\x40\x30
 0: abc@0
 1: abc
    abc\1000
 0: abc@0
 1: abc
    abc\100\x30
 0: abc@0
 1: abc
    abc\100\060
 0: abc@0
 1: abc
    abc\100\60
 0: abc@0
 1: abc
    
/^(A)(B)(C)(D)(E)(F)(G)(H)(I)\8\9$/
    ABCDEFGHIHI 
 0: ABCDEFGHIHI
 1: A
 2: B
 3: C
 4: D
 5: E
 6: F
 7: G
 8: H
 9: I

/^[A\8B\9C]+$/
    A8B9C
 0: A8B9C
\= Expect no match 
    A8B9C\x00
No match

/(a)(b)(c)(d)(e)(f)(g)(h)(i)(j)(k)(l)\12\123/
    abcdefghijkllS
 0: abcdefghijkllS
 1: a
 2: b
 3: c
 4: d
 5: e
 6: f
 7: g
 8: h
 9: i
10: j
11: k
12: l

/(a)(b)(c)(d)(e)(f)(g)(h)(i)(j)(k)\12\123/
    abcdefghijk\12S
 0: abcdefghijk\x0aS
 1: a
 2: b
 3: c
 4: d
 5: e
 6: f
 7: g
 8: h
 9: i
10: j
11: k

/a{0}bc/
    bc
 0: bc

/(a|(bc)){0,0}?xyz/
    xyz
 0: xyz

/abc[\10]de/
    abc\010de
 0: abc\x08de

/abc[\1]de/
    abc\1de
 0: abc\x01de

/(abc)[\1]de/
    abc\1de
 0: abc\x01de
 1: abc

/(?s)a.b/
    a\nb
 0: a\x0ab

/^([^a])([^\b])([^c]*)([^d]{3,4})/
    baNOTccccd
 0: baNOTcccc
 1: b
 2: a
 3: NOT
 4: cccc
    baNOTcccd
 0: baNOTccc
 1: b
 2: a
 3: NOT
 4: ccc
    baNOTccd
 0: baNOTcc
 1: b
 2: a
 3: NO
 4: Tcc
    bacccd
 0: baccc
 1: b
 2: a
 3: 
 4: ccc
\= Expect no match
    anything
No match
    b\bc   
No match
    baccd
No match

/[^a]/
    Abc
 0: A
  
/[^a]/i
    Abc 
 0: b

/[^a]+/
    AAAaAbc
 0: AAA
  
/[^a]+/i
    AAAaAbc 
 0: bc

/[^a]+/
    bbb\nccc
 0: bbb\x0accc
   
/[^k]$/
    abc
 0: c
\= Expect no match
    abk   
No match
   
/[^k]{2,3}$/
    abc
 0: abc
    kbc
 0: bc
    kabc 
 0: abc
\= Expect no match
    abk
No match
    akb
No match
    akk 
No match

/^\d{8,}\@.+[^k]$/
    12345678\@a.b.c.d
 0: 12345678@a.b.c.d
    123456789\@x.y.z
 0: 123456789@x.y.z
\= Expect no match
    12345678\@x.y.uk
No match
    1234567\@a.b.c.d       
No match

/(a)\1{8,}/
    aaaaaaaaa
 0: aaaaaaaaa
 1: a
    aaaaaaaaaa
 0: aaaaaaaaaa
 1: a
\= Expect no match
    aaaaaaa   
No match

/[^a]/
    aaaabcd
 0: b
    aaAabcd 
 0: A

/[^a]/i
    aaaabcd
 0: b
    aaAabcd 
 0: b

/[^az]/
    aaaabcd
 0: b
    aaAabcd 
 0: A

/[^az]/i
    aaaabcd
 0: b
    aaAabcd 
 0: b

/\000\001\002\003\004\005\006\007\010\011\012\013\014\015\016\017\020\021\022\023\024\025\026\027\030\031\032\033\034\035\036\037\040\041\042\043\044\045\046\047\050\051\052\053\054\055\056\057\060\061\062\063\064\065\066\067\070\071\072\073\074\075\076\077\100\101\102\103\104\105\106\107\110\111\112\113\114\115\116\117\120\121\122\123\124\125\126\127\130\131\132\133\134\135\136\137\140\141\142\143\144\145\146\147\150\151\152\153\154\155\156\157\160\161\162\163\164\165\166\167\170\171\172\173\174\175\176\177\200\201\202\203\204\205\206\207\210\211\212\213\214\215\216\217\220\221\222\223\224\225\226\227\230\231\232\233\234\235\236\237\240\241\242\243\244\245\246\247\250\251\252\253\254\255\256\257\260\261\262\263\264\265\266\267\270\271\272\273\274\275\276\277\300\301\302\303\304\305\306\307\310\311\312\313\314\315\316\317\320\321\322\323\324\325\326\327\330\331\332\333\334\335\336\337\340\341\342\343\344\345\346\347\350\351\352\353\354\355\356\357\360\361\362\363\364\365\366\367\370\371\372\373\374\375\376\377/
 \000\001\002\003\004\005\006\007\010\011\012\013\014\015\016\017\020\021\022\023\024\025\026\027\030\031\032\033\034\035\036\037\040\041\042\043\044\045\046\047\050\051\052\053\054\055\056\057\060\061\062\063\064\065\066\067\070\071\072\073\074\075\076\077\100\101\102\103\104\105\106\107\110\111\112\113\114\115\116\117\120\121\122\123\124\125\126\127\130\131\132\133\134\135\136\137\140\141\142\143\144\145\146\147\150\151\152\153\154\155\156\157\160\161\162\163\164\165\166\167\170\171\172\173\174\175\176\177\200\201\202\203\204\205\206\207\210\211\212\213\214\215\216\217\220\221\222\223\224\225\226\227\230\231\232\233\234\235\236\237\240\241\242\243\244\245\246\247\250\251\252\253\254\255\256\257\260\261\262\263\264\265\266\267\270\271\272\273\274\275\276\277\300\301\302\303\304\305\306\307\310\311\312\313\314\315\316\317\320\321\322\323\324\325\326\327\330\331\332\333\334\335\336\337\340\341\342\343\344\345\346\347\350\351\352\353\354\355\356\357\360\361\362\363\364\365\366\367\370\371\372\373\374\375\376\377
 0: \x00\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f !"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~\x7f\x80\x81\x82\x83\x84\x85\x86\x87\x88\x89\x8a\x8b\x8c\x8d\x8e\x8f\x90\x91\x92\x93\x94\x95\x96\x97\x98\x99\x9a\x9b\x9c\x9d\x9e\x9f\xa0\xa1\xa2\xa3\xa4\xa5\xa6\xa7\xa8\xa9\xaa\xab\xac\xad\xae\xaf\xb0\xb1\xb2\xb3\xb4\xb5\xb6\xb7\xb8\xb9\xba\xbb\xbc\xbd\xbe\xbf\xc0\xc1\xc2\xc3\xc4\xc5\xc6\xc7\xc8\xc9\xca\xcb\xcc\xcd\xce\xcf\xd0\xd1\xd2\xd3\xd4\xd5\xd6\xd7\xd8\xd9\xda\xdb\xdc\xdd\xde\xdf\xe0\xe1\xe2\xe3\xe4\xe5\xe6\xe7\xe8\xe9\xea\xeb\xec\xed\xee\xef\xf0\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9\xfa\xfb\xfc\xfd\xfe\xff

/P[^*]TAIRE[^*]{1,6}?LL/
    xxxxxxxxxxxPSTAIREISLLxxxxxxxxx
 0: PSTAIREISLL

/P[^*]TAIRE[^*]{1,}?LL/
    xxxxxxxxxxxPSTAIREISLLxxxxxxxxx
 0: PSTAIREISLL

/(\.\d\d[1-9]?)\d+/
    1.230003938
 0: .230003938
 1: .23
    1.875000282   
 0: .875000282
 1: .875
    1.235  
 0: .235
 1: .23
                  
/(\.\d\d((?=0)|\d(?=\d)))/
    1.230003938      
 0: .23
 1: .23
 2: 
    1.875000282
 0: .875
 1: .875
 2: 5
\= Expect no match 
    1.235 
No match
    
/a(?)b/
    ab 
 0: ab
 
/\b(foo)\s+(\w+)/i
    Food is on the foo table
 0: foo table
 1: foo
 2: table
    
/foo(.*)bar/
    The food is under the bar in the barn.
 0: food is under the bar in the bar
 1: d is under the bar in the 
    
/foo(.*?)bar/
    The food is under the bar in the barn.
 0: food is under the bar
 1: d is under the 

/(.*)(\d*)/
    I have 2 numbers: 53147
 0: I have 2 numbers: 53147
 1: I have 2 numbers: 53147
 2: 
    
/(.*)(\d+)/
    I have 2 numbers: 53147
 0: I have 2 numbers: 53147
 1: I have 2 numbers: 5314
 2: 7
 
/(.*?)(\d*)/
    I have 2 numbers: 53147
 0: 
 1: 
 2: 

/(.*?)(\d+)/
    I have 2 numbers: 53147
 0: I have 2
 1: I have 
 2: 2

/(.*)(\d+)$/
    I have 2 numbers: 53147
 0: I have 2 numbers: 53147
 1: I have 2 numbers: 5314
 2: 7

/(.*?)(\d+)$/
    I have 2 numbers: 53147
 0: I have 2 numbers: 53147
 1: I have 2 numbers: 
 2: 53147

/(.*)\b(\d+)$/
    I have 2 numbers: 53147
 0: I have 2 numbers: 53147
 1: I have 2 numbers: 
 2: 53147

/(.*\D)(\d+)$/
    I have 2 numbers: 53147
 0: I have 2 numbers: 53147
 1: I have 2 numbers: 
 2: 53147

/^\D*(?!123)/
    ABC123
 0: AB
     
/^(\D*)(?=\d)(?!123)/
    ABC445
 0: ABC
 1: ABC
\= Expect no match
    ABC123
No match
    
/^[W-]46]/
    W46]789 
 0: W46]
    -46]789
 0: -46]
\= Expect no match
    Wall
No match
    Zebra
No match
    42
No match
    [abcd] 
No match
    ]abcd[
No match
       
/^[W-\]46]/
    W46]789 
 0: W
    Wall
 0: W
    Zebra
 0: Z
    Xylophone  
 0: X
    42
 0: 4
    [abcd] 
 0: [
    ]abcd[
 0: ]
    \\backslash 
 0: \
\= Expect no match
    -46]789
No match
    well
No match
    
/\d\d\/\d\d\/\d\d\d\d/
    01/01/2000
 0: 01/01/2000

/word (?:[a-zA-Z0-9]+ ){0,10}otherword/
    word cat dog elephant mussel cow horse canary baboon snake shark otherword
 0: word cat dog elephant mussel cow horse canary baboon snake shark otherword
\= Expect no match
    word cat dog elephant mussel cow horse canary baboon snake shark
No match

/word (?:[a-zA-Z0-9]+ ){0,300}otherword/
\= Expect no match
    word cat dog elephant mussel cow horse canary baboon snake shark the quick brown fox and the lazy dog and several other words getting close to thirty by now I hope
No match

/^(a){0,0}/
    bcd
 0: 
    abc
 0: 
    aab     
 0: 

/^(a){0,1}/
    bcd
 0: 
    abc
 0: a
 1: a
    aab  
 0: a
 1: a

/^(a){0,2}/
    bcd
 0: 
    abc
 0: a
 1: a
    aab  
 0: aa
 1: a

/^(a){0,3}/
    bcd
 0: 
    abc
 0: a
 1: a
    aab
 0: aa
 1: a
    aaa   
 0: aaa
 1: a

/^(a){0,}/
    bcd
 0: 
    abc
 0: a
 1: a
    aab
 0: aa
 1: a
    aaa
 0: aaa
 1: a
    aaaaaaaa    
 0: aaaaaaaa
 1: a

/^(a){1,1}/
    abc
 0: a
 1: a
    aab  
 0: a
 1: a
\= Expect no match
    bcd
No match

/^(a){1,2}/
    abc
 0: a
 1: a
    aab  
 0: aa
 1: a
\= Expect no match
    bcd
No match

/^(a){1,3}/
    abc
 0: a
 1: a
    aab
 0: aa
 1: a
    aaa   
 0: aaa
 1: a
\= Expect no match
    bcd
No match

/^(a){1,}/
    abc
 0: a
 1: a
    aab
 0: aa
 1: a
    aaa
 0: aaa
 1: a
    aaaaaaaa    
 0: aaaaaaaa
 1: a
\= Expect no match
    bcd
No match

/.*\.gif/
    borfle\nbib.gif\nno
 0: bib.gif

/.{0,}\.gif/
    borfle\nbib.gif\nno
 0: bib.gif

/.*\.gif/m
    borfle\nbib.gif\nno
 0: bib.gif

/.*\.gif/s
    borfle\nbib.gif\nno
 0: borfle\x0abib.gif

/.*\.gif/ms
    borfle\nbib.gif\nno
 0: borfle\x0abib.gif
    
/.*$/
    borfle\nbib.gif\nno
 0: no

/.*$/m
    borfle\nbib.gif\nno
 0: borfle

/.*$/s
    borfle\nbib.gif\nno
 0: borfle\x0abib.gif\x0ano

/.*$/ms
    borfle\nbib.gif\nno
 0: borfle\x0abib.gif\x0ano
    
/.*$/
    borfle\nbib.gif\nno\n
 0: no

/.*$/m
    borfle\nbib.gif\nno\n
 0: borfle

/.*$/s
    borfle\nbib.gif\nno\n
 0: borfle\x0abib.gif\x0ano\x0a

/.*$/ms
    borfle\nbib.gif\nno\n
 0: borfle\x0abib.gif\x0ano\x0a
    
/(.*X|^B)/
    abcde\n1234Xyz
 0: 1234X
 1: 1234X
    BarFoo 
 0: B
 1: B
\= Expect no match
    abcde\nBar  
No match

/(.*X|^B)/m
    abcde\n1234Xyz
 0: 1234X
 1: 1234X
    BarFoo 
 0: B
 1: B
    abcde\nBar  
 0: B
 1: B

/(.*X|^B)/s
    abcde\n1234Xyz
 0: abcde\x0a1234X
 1: abcde\x0a1234X
    BarFoo 
 0: B
 1: B
\= Expect no match
    abcde\nBar  
No match

/(.*X|^B)/ms
    abcde\n1234Xyz
 0: abcde\x0a1234X
 1: abcde\x0a1234X
    BarFoo 
 0: B
 1: B
    abcde\nBar  
 0: B
 1: B

/(?s)(.*X|^B)/
    abcde\n1234Xyz
 0: abcde\x0a1234X
 1: abcde\x0a1234X
    BarFoo 
 0: B
 1: B
\= Expect no match 
    abcde\nBar  
No match

/(?s:.*X|^B)/
    abcde\n1234Xyz
 0: abcde\x0a1234X
    BarFoo 
 0: B
\= Expect no match 
    abcde\nBar  
No match

/^.*B/
\= Expect no match
    abc\nB
No match
     
/(?s)^.*B/
    abc\nB
 0: abc\x0aB

/(?m)^.*B/
    abc\nB
 0: B
     
/(?ms)^.*B/
    abc\nB
 0: abc\x0aB

/(?ms)^B/
    abc\nB
 0: B

/(?s)B$/
    B\n
 0: B

/^[0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9]/
    123456654321
 0: 123456654321
  
/^\d\d\d\d\d\d\d\d\d\d\d\d/
    123456654321 
 0: 123456654321

/^[\d][\d][\d][\d][\d][\d][\d][\d][\d][\d][\d][\d]/
    123456654321
 0: 123456654321
  
/^[abc]{12}/
    abcabcabcabc
 0: abcabcabcabc
    
/^[a-c]{12}/
    abcabcabcabc
 0: abcabcabcabc
    
/^(a|b|c){12}/
    abcabcabcabc 
 0: abcabcabcabc
 1: c

/^[abcdefghijklmnopqrstuvwxy0123456789]/
    n
 0: n
\= Expect no match 
    z 
No match

/abcde{0,0}/
    abcd
 0: abcd
\= Expect no match
    abce  
No match

/ab[cd]{0,0}e/
    abe
 0: abe
\= Expect no match
    abcde 
No match
    
/ab(c){0,0}d/
    abd
 0: abd
\= Expect no match
    abcd   
No match

/a(b*)/
    a
 0: a
 1: 
    ab
 0: ab
 1: b
    abbbb
 0: abbbb
 1: bbbb
\= Expect no match
    bbbbb    
No match
    
/ab\d{0}e/
    abe
 0: abe
\= Expect no match
    ab1e   
No match
    
/"([^\\"]+|\\.)*"/
    the \"quick\" brown fox
 0: "quick"
 1: quick
    \"the \\\"quick\\\" brown fox\" 
 0: "the \"quick\" brown fox"
 1:  brown fox

/.*?/g,aftertext
    abc
 0: 
 0+ abc
 0: a
 0+ bc
 0: 
 0+ bc
 0: b
 0+ c
 0: 
 0+ c
 0: c
 0+ 
 0: 
 0+ 
  
/\b/g,aftertext
    abc 
 0: 
 0+ abc
 0: 
 0+ 

/\b/g,aftertext
    abc 
 0: 
 0+ abc
 0: 
 0+ 

//g
    abc
 0: 
 0: 
 0: 
 0: 

/<tr([\w\W\s\d][^<>]{0,})><TD([\w\W\s\d][^<>]{0,})>([\d]{0,}\.)(.*)((<BR>([\w\W\s\d][^<>]{0,})|[\s]{0,}))<\/a><\/TD><TD([\w\W\s\d][^<>]{0,})>([\w\W\s\d][^<>]{0,})<\/TD><TD([\w\W\s\d][^<>]{0,})>([\w\W\s\d][^<>]{0,})<\/TD><\/TR>/is
  <TR BGCOLOR='#DBE9E9'><TD align=left valign=top>43.<a href='joblist.cfm?JobID=94 6735&Keyword='>Word Processor<BR>(N-1286)</a></TD><TD align=left valign=top>Lega lstaff.com</TD><TD align=left valign=top>CA - Statewide</TD></TR>
 0: <TR BGCOLOR='#DBE9E9'><TD align=left valign=top>43.<a href='joblist.cfm?JobID=94 6735&Keyword='>Word Processor<BR>(N-1286)</a></TD><TD align=left valign=top>Lega lstaff.com</TD><TD align=left valign=top>CA - Statewide</TD></TR>
 1:  BGCOLOR='#DBE9E9'
 2:  align=left valign=top
 3: 43.
 4: <a href='joblist.cfm?JobID=94 6735&Keyword='>Word Processor<BR>(N-1286)
 5: 
 6: 
 7: <unset>
 8:  align=left valign=top
 9: Lega lstaff.com
10:  align=left valign=top
11: CA - Statewide

/a[^a]b/
    acb
 0: acb
    a\nb
 0: a\x0ab
    
/a.b/
    acb
 0: acb
\= Expect no match 
    a\nb   
No match
    
/a[^a]b/s
    acb
 0: acb
    a\nb  
 0: a\x0ab
    
/a.b/s
    acb
 0: acb
    a\nb  
 0: a\x0ab

/^(b+?|a){1,2}?c/
    bac
 0: bac
 1: a
    bbac
 0: bbac
 1: a
    bbbac
 0: bbbac
 1: a
    bbbbac
 0: bbbbac
 1: a
    bbbbbac 
 0: bbbbbac
 1: a

/^(b+|a){1,2}?c/
    bac
 0: bac
 1: a
    bbac
 0: bbac
 1: a
    bbbac
 0: bbbac
 1: a
    bbbbac
 0: bbbbac
 1: a
    bbbbbac 
 0: bbbbbac
 1: a
    
/(?!\A)x/m
    a\bx\n
 0: x
    a\nx\n
 0: x
\= Expect no match     
    x\nb\n
No match
    
/(A|B)*?CD/
    CD 
 0: CD
    
/(A|B)*CD/
    CD 
 0: CD

/(AB)*?\1/
    ABABAB
 0: ABAB
 1: AB

/(AB)*\1/
    ABABAB
 0: ABABAB
 1: AB
    
/(?<!bar)foo/
    foo
 0: foo
    catfood
 0: foo
    arfootle
 0: foo
    rfoosh
 0: foo
\= Expect no match
    barfoo
No match
    towbarfoo
No match

/\w{3}(?<!bar)foo/
    catfood
 0: catfoo
\= Expect no match
    foo
No match
    barfoo
No match
    towbarfoo
No match

/(?<=(foo)a)bar/
    fooabar
 0: bar
 1: foo
\= Expect no match
    bar
No match
    foobbar
No match
      
/\Aabc\z/m
    abc
 0: abc
\= Expect no match
    abc\n   
No match
    qqq\nabc
No match
    abc\nzzz
No match
    qqq\nabc\nzzz
No match

/(?>.*\/)foo/
    /this/is/a/very/long/line/in/deed/with/very/many/slashes/in/and/foo
 0: /this/is/a/very/long/line/in/deed/with/very/many/slashes/in/and/foo
\= Expect no match     
    /this/is/a/very/long/line/in/deed/with/very/many/slashes/in/it/you/see/
No match

/(?>(\.\d\d[1-9]?))\d+/
    1.230003938
 0: .230003938
 1: .23
    1.875000282
 0: .875000282
 1: .875
\= Expect no match 
    1.235 
No match

/^((?>\w+)|(?>\s+))*$/
    now is the time for all good men to come to the aid of the party
 0: now is the time for all good men to come to the aid of the party
 1: party
\= Expect no match
    this is not a line with only words and spaces!
No match
    
/(\d+)(\w)/
    12345a
 0: 12345a
 1: 12345
 2: a
    12345+ 
 0: 12345
 1: 1234
 2: 5

/((?>\d+))(\w)/
    12345a
 0: 12345a
 1: 12345
 2: a
\= Expect no match
    12345+ 
No match

/(?>a+)b/
    aaab
 0: aaab

/((?>a+)b)/
    aaab
 0: aaab
 1: aaab

/(?>(a+))b/
    aaab
 0: aaab
 1: aaa

/(?>b)+/
    aaabbbccc
 0: bbb

/(?>a+|b+|c+)*c/
    aaabbbbccccd
 0: aaabbbbc

/((?>[^()]+)|\([^()]*\))+/
    ((abc(ade)ufh()()x
 0: abc(ade)ufh()()x
 1: x
    
/\(((?>[^()]+)|\([^()]+\))+\)/
    (abc)
 0: (abc)
 1: abc
    (abc(def)xyz)
 0: (abc(def)xyz)
 1: xyz
\= Expect no match
    ((()aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa   
No match

/a(?-i)b/i
    ab
 0: ab
    Ab
 0: Ab
\= Expect no match 
    aB
No match
    AB
No match
        
/(a (?x)b c)d e/
    a bcd e
 0: a bcd e
 1: a bc
\= Expect no match
    a b cd e
No match
    abcd e   
No match
    a bcde 
No match
 
/(a b(?x)c d (?-x)e f)/
    a bcde f
 0: a bcde f
 1: a bcde f
\= Expect no match
    abcdef  
No match

/(a(?i)b)c/
    abc
 0: abc
 1: ab
    aBc
 0: aBc
 1: aB
\= Expect no match
    abC
No match
    aBC  
No match
    Abc
No match
    ABc
No match
    ABC
No match
    AbC
No match
    
/a(?i:b)c/
    abc
 0: abc
    aBc
 0: aBc
\= Expect no match 
    ABC
No match
    abC
No match
    aBC
No match
    
/a(?i:b)*c/
    aBc
 0: aBc
    aBBc
 0: aBBc
\= Expect no match 
    aBC
No match
    aBBC
No match
    
/a(?=b(?i)c)\w\wd/
    abcd
 0: abcd
    abCd
 0: abCd
\= Expect no match
    aBCd
No match
    abcD     
No match
    
/(?s-i:more.*than).*million/i
    more than million
 0: more than million
    more than MILLION
 0: more than MILLION
    more \n than Million 
 0: more \x0a than Million
\= Expect no match
    MORE THAN MILLION    
No match
    more \n than \n million 
No match

/(?:(?s-i)more.*than).*million/i
    more than million
 0: more than million
    more than MILLION
 0: more than MILLION
    more \n than Million 
 0: more \x0a than Million
\= Expect no match
    MORE THAN MILLION    
No match
    more \n than \n million 
No match
    
/(?>a(?i)b+)+c/
    abc
 0: abc
    aBbc
 0: aBbc
    aBBc 
 0: aBBc
\= Expect no match
    Abc
No match
    abAb    
No match
    abbC 
No match
    
/(?=a(?i)b)\w\wc/
    abc
 0: abc
    aBc
 0: aBc
\= Expect no match
    Ab 
No match
    abC
No match
    aBC     
No match
    
/(?<=a(?i)b)(\w\w)c/
    abxxc
 0: xxc
 1: xx
    aBxxc
 0: xxc
 1: xx
\= Expect no match
    Abxxc
No match
    ABxxc
No match
    abxxC      
No match

/(?:(a)|b)(?(1)A|B)/
    aA
 0: aA
 1: a
    bB
 0: bB
\= Expect no match
    aB
No match
    bA    
No match

/^(a)?(?(1)a|b)+$/
    aa
 0: aa
 1: a
    b
 0: b
    bb  
 0: bb
\= Expect no match
    ab   
No match
    
# Perl gets this next one wrong if the pattern ends with $; in that case it
# fails to match "12". 

/^(?(?=abc)\w{3}:|\d\d)/
    abc:
 0: abc:
    12
 0: 12
    123
 0: 12
\= Expect no match
    xyz    
No match

/^(?(?!abc)\d\d|\w{3}:)$/
    abc:
 0: abc:
    12
 0: 12
\= Expect no match
    123
No match
    xyz    
No match
    
/(?(?<=foo)bar|cat)/
    foobar
 0: bar
    cat
 0: cat
    fcat
 0: cat
    focat   
 0: cat
\= Expect no match
    foocat  
No match

/(?(?<!foo)cat|bar)/
    foobar
 0: bar
    cat
 0: cat
    fcat
 0: cat
    focat   
 0: cat
\= Expect no match
    foocat  
No match

/( \( )? [^()]+ (?(1) \) |) /x
    abcd
 0: abcd
    (abcd)
 0: (abcd)
 1: (
    the quick (abcd) fox
 0: the quick 
    (abcd   
 0: abcd

/( \( )? [^()]+ (?(1) \) ) /x
    abcd
 0: abcd
    (abcd)
 0: (abcd)
 1: (
    the quick (abcd) fox
 0: the quick 
    (abcd   
 0: abcd

/^(?(2)a|(1)(2))+$/
    12
 0: 12
 1: 1
 2: 2
    12a
 0: 12a
 1: 1
 2: 2
    12aa
 0: 12aa
 1: 1
 2: 2
\= Expect no match
    1234    
No match

/((?i)blah)\s+\1/
    blah blah
 0: blah blah
 1: blah
    BLAH BLAH
 0: BLAH BLAH
 1: BLAH
    Blah Blah
 0: Blah Blah
 1: Blah
    blaH blaH
 0: blaH blaH
 1: blaH
\= Expect no match
    blah BLAH
No match
    Blah blah      
No match
    blaH blah 
No match

/((?i)blah)\s+(?i:\1)/
    blah blah
 0: blah blah
 1: blah
    BLAH BLAH
 0: BLAH BLAH
 1: BLAH
    Blah Blah
 0: Blah Blah
 1: Blah
    blaH blaH
 0: blaH blaH
 1: blaH
    blah BLAH
 0: blah BLAH
 1: blah
    Blah blah      
 0: Blah blah
 1: Blah
    blaH blah 
 0: blaH blah
 1: blaH

/((?i)blah)\s+(?m)A(?i:\1)/
    blah ABLAH
 0: blah ABLAH
 1: blah
\= Expect no match
    blah aBLAH
No match

/(?>a*)*/
    a
 0: a
    aa
 0: aa
    aaaa
 0: aaaa
    
/(abc|)+/
    abc
 0: abc
 1: 
    abcabc
 0: abcabc
 1: 
    abcabcabc
 0: abcabcabc
 1: 
    xyz      
 0: 
 1: 

/([a]*)*/
    a
 0: a
 1: 
    aaaaa 
 0: aaaaa
 1: 
 
/([ab]*)*/
    a
 0: a
 1: 
    b
 0: b
 1: 
    ababab
 0: ababab
 1: 
    aaaabcde
 0: aaaab
 1: 
    bbbb    
 0: bbbb
 1: 
 
/([^a]*)*/
    b
 0: b
 1: 
    bbbb
 0: bbbb
 1: 
    aaa   
 0: 
 1: 
 
/([^ab]*)*/
    cccc
 0: cccc
 1: 
    abab  
 0: 
 1: 
 
/([a]*?)*/
    a
 0: 
 1: 
    aaaa 
 0: 
 1: 
 
/([ab]*?)*/
    a
 0: 
 1: 
    b
 0: 
 1: 
    abab
 0: 
 1: 
    baba   
 0: 
 1: 
 
/([^a]*?)*/
    b
 0: 
 1: 
    bbbb
 0: 
 1: 
    aaa   
 0: 
 1: 
 
/([^ab]*?)*/
    c
 0: 
 1: 
    cccc
 0: 
 1: 
    baba   
 0: 
 1: 
 
/(?>a*)*/
    a
 0: a
    aaabcde 
 0: aaa
 
/((?>a*))*/
    aaaaa
 0: aaaaa
 1: 
    aabbaa 
 0: aa
 1: 
 
/((?>a*?))*/
    aaaaa
 0: 
 1: 
    aabbaa 
 0: 
 1: 

/(?(?=[^a-z]+[a-z])  \d{2}-[a-z]{3}-\d{2}  |  \d{2}-\d{2}-\d{2} ) /x
    12-sep-98
 0: 12-sep-98
    12-09-98
 0: 12-09-98
\= Expect no match
    sep-12-98
No match
        
/(?<=(foo))bar\1/
    foobarfoo
 0: barfoo
 1: foo
    foobarfootling 
 0: barfoo
 1: foo
\= Expect no match
    foobar
No match
    barfoo   
No match

/(?i:saturday|sunday)/
    saturday
 0: saturday
    sunday
 0: sunday
    Saturday
 0: Saturday
    Sunday
 0: Sunday
    SATURDAY
 0: SATURDAY
    SUNDAY
 0: SUNDAY
    SunDay
 0: SunDay
    
/(a(?i)bc|BB)x/
    abcx
 0: abcx
 1: abc
    aBCx
 0: aBCx
 1: aBC
    bbx
 0: bbx
 1: bb
    BBx
 0: BBx
 1: BB
\= Expect no match
    abcX
No match
    aBCX
No match
    bbX
No match
    BBX               
No match

/^([ab](?i)[cd]|[ef])/
    ac
 0: ac
 1: ac
    aC
 0: aC
 1: aC
    bD
 0: bD
 1: bD
    elephant
 0: e
 1: e
    Europe 
 0: E
 1: E
    frog
 0: f
 1: f
    France
 0: F
 1: F
\= Expect no match
    Africa     
No match

/^(ab|a(?i)[b-c](?m-i)d|x(?i)y|z)/
    ab
 0: ab
 1: ab
    aBd
 0: aBd
 1: aBd
    xy
 0: xy
 1: xy
    xY
 0: xY
 1: xY
    zebra
 0: z
 1: z
    Zambesi
 0: Z
 1: Z
\= Expect no match
    aCD  
No match
    XY  
No match

/(?<=foo\n)^bar/m
    foo\nbar
 0: bar
\= Expect no match
    bar
No match
    baz\nbar   
No match

/(?<=(?<!foo)bar)baz/
    barbaz
 0: baz
    barbarbaz 
 0: baz
    koobarbaz 
 0: baz
\= Expect no match
    baz
No match
    foobarbaz 
No match

# The cases of aaaa and aaaaaa are missed out below because Perl does things
# differently. We know that odd, and maybe incorrect, things happen with
# recursive references in Perl, as far as 5.11.3 - see some stuff in test #2.

/^(a\1?){4}$/
    aaaaa
 0: aaaaa
 1: a
    aaaaaaa
 0: aaaaaaa
 1: a
    aaaaaaaaaa
 0: aaaaaaaaaa
 1: aaaa
\= Expect no match
    a
No match
    aa
No match
    aaa
No match
    aaaaaaaa
No match
    aaaaaaaaa
No match
    aaaaaaaaaaa
No match
    aaaaaaaaaaaa
No match
    aaaaaaaaaaaaa
No match
    aaaaaaaaaaaaaa
No match
    aaaaaaaaaaaaaaa
No match
    aaaaaaaaaaaaaaaa
No match

/^(a\1?)(a\1?)(a\2?)(a\3?)$/
    aaaa
 0: aaaa
 1: a
 2: a
 3: a
 4: a
    aaaaa
 0: aaaaa
 1: a
 2: aa
 3: a
 4: a
    aaaaaa
 0: aaaaaa
 1: a
 2: aa
 3: a
 4: aa
    aaaaaaa
 0: aaaaaaa
 1: a
 2: aa
 3: aaa
 4: a
    aaaaaaaaaa
 0: aaaaaaaaaa
 1: a
 2: aa
 3: aaa
 4: aaaa
\= Expect no match
    a
No match
    aa
No match
    aaa
No match
    aaaaaaaa
No match
    aaaaaaaaa
No match
    aaaaaaaaaaa
No match
    aaaaaaaaaaaa
No match
    aaaaaaaaaaaaa
No match
    aaaaaaaaaaaaaa
No match
    aaaaaaaaaaaaaaa
No match
    aaaaaaaaaaaaaaaa               
No match

# The following tests are taken from the Perl 5.005 test suite; some of them
# are compatible with 5.004, but I'd rather not have to sort them out.

/abc/
    abc
 0: abc
    xabcy
 0: abc
    ababc
 0: abc
\= Expect no match
    xbc
No match
    axc
No match
    abx
No match

/ab*c/
    abc
 0: abc

/ab*bc/
    abc
 0: abc
    abbc
 0: abbc
    abbbbc
 0: abbbbc

/.{1}/
    abbbbc
 0: a

/.{3,4}/
    abbbbc
 0: abbb

/ab{0,}bc/
    abbbbc
 0: abbbbc

/ab+bc/
    abbc
 0: abbc
\= Expect no match
    abc
No match
    abq
No match

/ab{1,}bc/

/ab+bc/
    abbbbc
 0: abbbbc

/ab{1,}bc/
    abbbbc
 0: abbbbc

/ab{1,3}bc/
    abbbbc
 0: abbbbc

/ab{3,4}bc/
    abbbbc
 0: abbbbc

/ab{4,5}bc/
\= Expect no match
    abq
No match
    abbbbc
No match

/ab?bc/
    abbc
 0: abbc
    abc
 0: abc

/ab{0,1}bc/
    abc
 0: abc

/ab?bc/

/ab?c/
    abc
 0: abc

/ab{0,1}c/
    abc
 0: abc

/^abc$/
    abc
 0: abc
\= Expect no match
    abbbbc
No match
    abcc
No match

/^abc/
    abcc
 0: abc

/^abc$/

/abc$/
    aabc
 0: abc
\= Expect no match
    aabcd
No match

/^/
    abc
 0: 

/$/
    abc
 0: 

/a.c/
    abc
 0: abc
    axc
 0: axc

/a.*c/
    axyzc
 0: axyzc

/a[bc]d/
    abd
 0: abd
\= Expect no match
    axyzd
No match
    abc
No match

/a[b-d]e/
    ace
 0: ace

/a[b-d]/
    aac
 0: ac

/a[-b]/
    a-
 0: a-

/a[b-]/
    a-
 0: a-

/a]/
    a]
 0: a]

/a[]]b/
    a]b
 0: a]b

/a[^bc]d/
    aed
 0: aed
\= Expect no match
    abd
No match
    abd
No match

/a[^-b]c/
    adc
 0: adc

/a[^]b]c/
    adc
 0: adc
    a-c
 0: a-c
\= Expect no match
    a]c
No match

/\ba\b/
    a-
 0: a
    -a
 0: a
    -a-
 0: a

/\by\b/
\= Expect no match
    xy
No match
    yz
No match
    xyz
No match

/\Ba\B/
\= Expect no match
    a-
No match
    -a
No match
    -a-
No match

/\By\b/
    xy
 0: y

/\by\B/
    yz
 0: y

/\By\B/
    xyz
 0: y

/\w/
    a
 0: a

/\W/
    -
 0: -
\= Expect no match
    a
No match

/a\sb/
    a b
 0: a b

/a\Sb/
    a-b
 0: a-b
\= Expect no match
    a b
No match

/\d/
    1
 0: 1

/\D/
    -
 0: -
\= Expect no match
    1
No match

/[\w]/
    a
 0: a

/[\W]/
    -
 0: -
\= Expect no match
    a
No match

/a[\s]b/
    a b
 0: a b

/a[\S]b/
    a-b
 0: a-b
\= Expect no match
    a b
No match

/[\d]/
    1
 0: 1

/[\D]/
    -
 0: -
\= Expect no match
    1
No match

/ab|cd/
    abc
 0: ab
    abcd
 0: ab

/()ef/
    def
 0: ef
 1: 

/$b/

/a\(b/
    a(b
 0: a(b

/a\(*b/
    ab
 0: ab
    a((b
 0: a((b

/a\\b/
    a\\b
 0: a\b

/((a))/
    abc
 0: a
 1: a
 2: a

/(a)b(c)/
    abc
 0: abc
 1: a
 2: c

/a+b+c/
    aabbabc
 0: abc

/a{1,}b{1,}c/
    aabbabc
 0: abc

/a.+?c/
    abcabc
 0: abc

/(a+|b)*/
    ab
 0: ab
 1: b

/(a+|b){0,}/
    ab
 0: ab
 1: b

/(a+|b)+/
    ab
 0: ab
 1: b

/(a+|b){1,}/
    ab
 0: ab
 1: b

/(a+|b)?/
    ab
 0: a
 1: a

/(a+|b){0,1}/
    ab
 0: a
 1: a

/[^ab]*/
    cde
 0: cde

/abc/
\= Expect no match
    b
No match

/a*/
    \
 0: 

/([abc])*d/
    abbbcd
 0: abbbcd
 1: c

/([abc])*bcd/
    abcd
 0: abcd
 1: a

/a|b|c|d|e/
    e
 0: e

/(a|b|c|d|e)f/
    ef
 0: ef
 1: e

/abcd*efg/
    abcdefg
 0: abcdefg

/ab*/
    xabyabbbz
 0: ab
    xayabbbz
 0: a

/(ab|cd)e/
    abcde
 0: cde
 1: cd

/[abhgefdc]ij/
    hij
 0: hij

/^(ab|cd)e/

/(abc|)ef/
    abcdef
 0: ef
 1: 

/(a|b)c*d/
    abcd
 0: bcd
 1: b

/(ab|ab*)bc/
    abc
 0: abc
 1: a

/a([bc]*)c*/
    abc
 0: abc
 1: bc

/a([bc]*)(c*d)/
    abcd
 0: abcd
 1: bc
 2: d

/a([bc]+)(c*d)/
    abcd
 0: abcd
 1: bc
 2: d

/a([bc]*)(c+d)/
    abcd
 0: abcd
 1: b
 2: cd

/a[bcd]*dcdcde/
    adcdcde
 0: adcdcde

/a[bcd]+dcdcde/
\= Expect no match
    abcde
No match
    adcdcde
No match

/(ab|a)b*c/
    abc
 0: abc
 1: ab

/((a)(b)c)(d)/
    abcd
 0: abcd
 1: abc
 2: a
 3: b
 4: d

/[a-zA-Z_][a-zA-Z0-9_]*/
    alpha
 0: alpha

/^a(bc+|b[eh])g|.h$/
    abh
 0: bh

/(bc+d$|ef*g.|h?i(j|k))/
    effgz
 0: effgz
 1: effgz
    ij
 0: ij
 1: ij
 2: j
    reffgz
 0: effgz
 1: effgz
\= Expect no match
    effg
No match
    bcdd
No match

/((((((((((a))))))))))/
    a
 0: a
 1: a
 2: a
 3: a
 4: a
 5: a
 6: a
 7: a
 8: a
 9: a
10: a

/((((((((((a))))))))))\10/
    aa
 0: aa
 1: a
 2: a
 3: a
 4: a
 5: a
 6: a
 7: a
 8: a
 9: a
10: a

/(((((((((a)))))))))/
    a
 0: a
 1: a
 2: a
 3: a
 4: a
 5: a
 6: a
 7: a
 8: a
 9: a

/multiple words of text/
\= Expect no match
    aa
No match
    uh-uh
No match

/multiple words/
    multiple words, yeah
 0: multiple words

/(.*)c(.*)/
    abcde
 0: abcde
 1: ab
 2: de

/\((.*), (.*)\)/
    (a, b)
 0: (a, b)
 1: a
 2: b

/[k]/

/abcd/
    abcd
 0: abcd

/a(bc)d/
    abcd
 0: abcd
 1: bc

/a[-]?c/
    ac
 0: ac

/(abc)\1/
    abcabc
 0: abcabc
 1: abc

/([a-c]*)\1/
    abcabc
 0: abcabc
 1: abc

/(a)|\1/
    a
 0: a
 1: a
    ab
 0: a
 1: a
\= Expect no match
    x
No match

/(([a-c])b*?\2)*/
    ababbbcbc
 0: ababb
 1: bb
 2: b

/(([a-c])b*?\2){3}/
    ababbbcbc
 0: ababbbcbc
 1: cbc
 2: c

/((\3|b)\2(a)x)+/
    aaaxabaxbaaxbbax
 0: bbax
 1: bbax
 2: b
 3: a

/((\3|b)\2(a)){2,}/
    bbaababbabaaaaabbaaaabba
 0: bbaaaabba
 1: bba
 2: b
 3: a

/abc/i
    ABC
 0: ABC
    XABCY
 0: ABC
    ABABC
 0: ABC
\= Expect no match
    aaxabxbaxbbx
No match
    XBC
No match
    AXC
No match
    ABX
No match

/ab*c/i
    ABC
 0: ABC

/ab*bc/i
    ABC
 0: ABC
    ABBC
 0: ABBC

/ab*?bc/i
    ABBBBC
 0: ABBBBC

/ab{0,}?bc/i
    ABBBBC
 0: ABBBBC

/ab+?bc/i
    ABBC
 0: ABBC

/ab+bc/i
\= Expect no match
    ABC
No match
    ABQ
No match

/ab{1,}bc/i

/ab+bc/i
    ABBBBC
 0: ABBBBC

/ab{1,}?bc/i
    ABBBBC
 0: ABBBBC

/ab{1,3}?bc/i
    ABBBBC
 0: ABBBBC

/ab{3,4}?bc/i
    ABBBBC
 0: ABBBBC

/ab{4,5}?bc/i
\= Expect no match
    ABQ
No match
    ABBBBC
No match

/ab??bc/i
    ABBC
 0: ABBC
    ABC
 0: ABC

/ab{0,1}?bc/i
    ABC
 0: ABC

/ab??bc/i

/ab??c/i
    ABC
 0: ABC

/ab{0,1}?c/i
    ABC
 0: ABC

/^abc$/i
    ABC
 0: ABC
\= Expect no match
    ABBBBC
No match
    ABCC
No match

/^abc/i
    ABCC
 0: ABC

/^abc$/i

/abc$/i
    AABC
 0: ABC

/^/i
    ABC
 0: 

/$/i
    ABC
 0: 

/a.c/i
    ABC
 0: ABC
    AXC
 0: AXC

/a.*?c/i
    AXYZC
 0: AXYZC

/a.*c/i
    AABC
 0: AABC
\= Expect no match
    AXYZD
No match

/a[bc]d/i
    ABD
 0: ABD

/a[b-d]e/i
    ACE
 0: ACE
\= Expect no match
    ABC
No match
    ABD
No match

/a[b-d]/i
    AAC
 0: AC

/a[-b]/i
    A-
 0: A-

/a[b-]/i
    A-
 0: A-

/a]/i
    A]
 0: A]

/a[]]b/i
    A]B
 0: A]B

/a[^bc]d/i
    AED
 0: AED

/a[^-b]c/i
    ADC
 0: ADC
\= Expect no match
    ABD
No match
    A-C
No match

/a[^]b]c/i
    ADC
 0: ADC

/ab|cd/i
    ABC
 0: AB
    ABCD
 0: AB

/()ef/i
    DEF
 0: EF
 1: 

/$b/i
\= Expect no match
    A]C
No match
    B
No match

/a\(b/i
    A(B
 0: A(B

/a\(*b/i
    AB
 0: AB
    A((B
 0: A((B

/a\\b/i
    A\\b
 0: A\b
    a\\B 
 0: a\B

/((a))/i
    ABC
 0: A
 1: A
 2: A

/(a)b(c)/i
    ABC
 0: ABC
 1: A
 2: C

/a+b+c/i
    AABBABC
 0: ABC

/a{1,}b{1,}c/i
    AABBABC
 0: ABC

/a.+?c/i
    ABCABC
 0: ABC

/a.*?c/i
    ABCABC
 0: ABC

/a.{0,5}?c/i
    ABCABC
 0: ABC

/(a+|b)*/i
    AB
 0: AB
 1: B

/(a+|b){0,}/i
    AB
 0: AB
 1: B

/(a+|b)+/i
    AB
 0: AB
 1: B

/(a+|b){1,}/i
    AB
 0: AB
 1: B

/(a+|b)?/i
    AB
 0: A
 1: A

/(a+|b){0,1}/i
    AB
 0: A
 1: A

/(a+|b){0,1}?/i
    AB
 0: 

/[^ab]*/i
    CDE
 0: CDE

/([abc])*d/i
    ABBBCD
 0: ABBBCD
 1: C

/([abc])*bcd/i
    ABCD
 0: ABCD
 1: A

/a|b|c|d|e/i
    E
 0: E

/(a|b|c|d|e)f/i
    EF
 0: EF
 1: E

/abcd*efg/i
    ABCDEFG
 0: ABCDEFG

/ab*/i
    XABYABBBZ
 0: AB
    XAYABBBZ
 0: A

/(ab|cd)e/i
    ABCDE
 0: CDE
 1: CD

/[abhgefdc]ij/i
    HIJ
 0: HIJ

/^(ab|cd)e/i
\= Expect no match
    ABCDE
No match

/(abc|)ef/i
    ABCDEF
 0: EF
 1: 

/(a|b)c*d/i
    ABCD
 0: BCD
 1: B

/(ab|ab*)bc/i
    ABC
 0: ABC
 1: A

/a([bc]*)c*/i
    ABC
 0: ABC
 1: BC

/a([bc]*)(c*d)/i
    ABCD
 0: ABCD
 1: BC
 2: D

/a([bc]+)(c*d)/i
    ABCD
 0: ABCD
 1: BC
 2: D

/a([bc]*)(c+d)/i
    ABCD
 0: ABCD
 1: B
 2: CD

/a[bcd]*dcdcde/i
    ADCDCDE
 0: ADCDCDE

/a[bcd]+dcdcde/i

/(ab|a)b*c/i
    ABC
 0: ABC
 1: AB

/((a)(b)c)(d)/i
    ABCD
 0: ABCD
 1: ABC
 2: A
 3: B
 4: D

/[a-zA-Z_][a-zA-Z0-9_]*/i
    ALPHA
 0: ALPHA

/^a(bc+|b[eh])g|.h$/i
    ABH
 0: BH

/(bc+d$|ef*g.|h?i(j|k))/i
    EFFGZ
 0: EFFGZ
 1: EFFGZ
    IJ
 0: IJ
 1: IJ
 2: J
    REFFGZ
 0: EFFGZ
 1: EFFGZ
\= Expect no match
    ADCDCDE
No match
    EFFG
No match
    BCDD
No match

/((((((((((a))))))))))/i
    A
 0: A
 1: A
 2: A
 3: A
 4: A
 5: A
 6: A
 7: A
 8: A
 9: A
10: A

/((((((((((a))))))))))\10/i
    AA
 0: AA
 1: A
 2: A
 3: A
 4: A
 5: A
 6: A
 7: A
 8: A
 9: A
10: A

/(((((((((a)))))))))/i
    A
 0: A
 1: A
 2: A
 3: A
 4: A
 5: A
 6: A
 7: A
 8: A
 9: A

/(?:(?:(?:(?:(?:(?:(?:(?:(?:(a))))))))))/i
    A
 0: A
 1: A

/(?:(?:(?:(?:(?:(?:(?:(?:(?:(a|b|c))))))))))/i
    C
 0: C
 1: C

/multiple words of text/i
\= Expect no match
    AA
No match
    UH-UH
No match

/multiple words/i
    MULTIPLE WORDS, YEAH
 0: MULTIPLE WORDS

/(.*)c(.*)/i
    ABCDE
 0: ABCDE
 1: AB
 2: DE

/\((.*), (.*)\)/i
    (A, B)
 0: (A, B)
 1: A
 2: B

/[k]/i

/abcd/i
    ABCD
 0: ABCD

/a(bc)d/i
    ABCD
 0: ABCD
 1: BC

/a[-]?c/i
    AC
 0: AC

/(abc)\1/i
    ABCABC
 0: ABCABC
 1: ABC

/([a-c]*)\1/i
    ABCABC
 0: ABCABC
 1: ABC

/a(?!b)./
    abad
 0: ad

/a(?=d)./
    abad
 0: ad

/a(?=c|d)./
    abad
 0: ad

/a(?:b|c|d)(.)/
    ace
 0: ace
 1: e

/a(?:b|c|d)*(.)/
    ace
 0: ace
 1: e

/a(?:b|c|d)+?(.)/
    ace
 0: ace
 1: e
    acdbcdbe
 0: acd
 1: d

/a(?:b|c|d)+(.)/
    acdbcdbe
 0: acdbcdbe
 1: e

/a(?:b|c|d){2}(.)/
    acdbcdbe
 0: acdb
 1: b

/a(?:b|c|d){4,5}(.)/
    acdbcdbe
 0: acdbcdb
 1: b

/a(?:b|c|d){4,5}?(.)/
    acdbcdbe
 0: acdbcd
 1: d

/a(?:b|c|d){6,7}(.)/
    acdbcdbe
 0: acdbcdbe
 1: e

/a(?:b|c|d){6,7}?(.)/
    acdbcdbe
 0: acdbcdbe
 1: e

/a(?:b|c|d){5,6}(.)/
    acdbcdbe
 0: acdbcdbe
 1: e

/a(?:b|c|d){5,6}?(.)/
    acdbcdbe
 0: acdbcdb
 1: b

/a(?:b|c|d){5,7}(.)/
    acdbcdbe
 0: acdbcdbe
 1: e

/a(?:b|c|d){5,7}?(.)/
    acdbcdbe
 0: acdbcdb
 1: b

/a(?:b|(c|e){1,2}?|d)+?(.)/
    ace
 0: ace
 1: c
 2: e

/^(.+)?B/
    AB
 0: AB
 1: A

/^([^a-z])|(\^)$/
    .
 0: .
 1: .

/^[<>]&/
    <&OUT
 0: <&

/^(a\1?){4}$/
    aaaaaaaaaa
 0: aaaaaaaaaa
 1: aaaa
\= Expect no match
    AB
No match
    aaaaaaaaa
No match
    aaaaaaaaaaa
No match

/^(a(?(1)\1)){4}$/
    aaaaaaaaaa
 0: aaaaaaaaaa
 1: aaaa
\= Expect no match
    aaaaaaaaa
No match
    aaaaaaaaaaa
No match

/(?<=a)b/
    ab
 0: b
\= Expect no match
    cb
No match
    b
No match

/(?<!c)b/
    ab
 0: b
    b
 0: b
    b
 0: b

/(?:..)*a/
    aba
 0: aba

/(?:..)*?a/
    aba
 0: a

/^(?:b|a(?=(.)))*\1/
    abc
 0: ab
 1: b

/^(){3,5}/
    abc
 0: 
 1: 

/^(a+)*ax/
    aax
 0: aax
 1: a

/^((a|b)+)*ax/
    aax
 0: aax
 1: a
 2: a

/^((a|bc)+)*ax/
    aax
 0: aax
 1: a
 2: a

/(a|x)*ab/
    cab
 0: ab

/(a)*ab/
    cab
 0: ab

/(?:(?i)a)b/
    ab
 0: ab

/((?i)a)b/
    ab
 0: ab
 1: a

/(?:(?i)a)b/
    Ab
 0: Ab

/((?i)a)b/
    Ab
 0: Ab
 1: A

/(?:(?i)a)b/
\= Expect no match
    cb
No match
    aB
No match

/((?i)a)b/

/(?i:a)b/
    ab
 0: ab

/((?i:a))b/
    ab
 0: ab
 1: a

/(?i:a)b/
    Ab
 0: Ab

/((?i:a))b/
    Ab
 0: Ab
 1: A

/(?i:a)b/
\= Expect no match
    aB
No match
    aB
No match

/((?i:a))b/

/(?:(?-i)a)b/i
    ab
 0: ab

/((?-i)a)b/i
    ab
 0: ab
 1: a

/(?:(?-i)a)b/i
    aB
 0: aB

/((?-i)a)b/i
    aB
 0: aB
 1: a

/(?:(?-i)a)b/i
    aB
 0: aB
\= Expect no match
    Ab
No match
    AB
No match

/(?-i:a)b/i
    ab
 0: ab

/((?-i:a))b/i
    ab
 0: ab
 1: a

/(?-i:a)b/i
    aB
 0: aB

/((?-i:a))b/i
    aB
 0: aB
 1: a

/(?-i:a)b/i
\= Expect no match
    AB
No match
    Ab
No match

/((?-i:a))b/i

/(?-i:a)b/i
    aB
 0: aB

/((?-i:a))b/i
    aB
 0: aB
 1: a

/(?-i:a)b/i
\= Expect no match
    Ab
No match
    AB
No match

/((?-i:a))b/i

/((?-i:a.))b/i
\= Expect no match
    AB
No match
    a\nB
No match

/((?s-i:a.))b/i
    a\nB
 0: a\x0aB
 1: a\x0a

/(?:c|d)(?:)(?:a(?:)(?:b)(?:b(?:))(?:b(?:)(?:b)))/
    cabbbb
 0: cabbbb

/(?:c|d)(?:)(?:aaaaaaaa(?:)(?:bbbbbbbb)(?:bbbbbbbb(?:))(?:bbbbbbbb(?:)(?:bbbbbbbb)))/
    caaaaaaaabbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
 0: caaaaaaaabbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb

/(ab)\d\1/i
    Ab4ab
 0: Ab4ab
 1: Ab
    ab4Ab
 0: ab4Ab
 1: ab

/foo\w*\d{4}baz/
    foobar1234baz
 0: foobar1234baz

/x(~~)*(?:(?:F)?)?/
    x~~
 0: x~~
 1: ~~

/^a(?#xxx){3}c/
    aaac
 0: aaac

/^a (?#xxx) (?#yyy) {3}c/x
    aaac
 0: aaac

/(?<![cd])b/
\= Expect no match
    B\nB
No match
    dbcb
No match

/(?<![cd])[ab]/
    dbaacb
 0: a

/(?<!(c|d))b/

/(?<!(c|d))[ab]/
    dbaacb
 0: a

/(?<!cd)[ab]/
    cdaccb
 0: b

/^(?:a?b?)*$/
    \
 0: 
    a
 0: a
    ab
 0: ab
    aaa   
 0: aaa
\= Expect no match
    dbcb
No match
    a--
No match
    aa-- 
No match

/((?s)^a(.))((?m)^b$)/
    a\nb\nc\n
 0: a\x0ab
 1: a\x0a
 2: \x0a
 3: b

/((?m)^b$)/
    a\nb\nc\n
 0: b
 1: b

/(?m)^b/
    a\nb\n
 0: b

/(?m)^(b)/
    a\nb\n
 0: b
 1: b

/((?m)^b)/
    a\nb\n
 0: b
 1: b

/\n((?m)^b)/
    a\nb\n
 0: \x0ab
 1: b

/((?s).)c(?!.)/
    a\nb\nc\n
 0: \x0ac
 1: \x0a
    a\nb\nc\n
 0: \x0ac
 1: \x0a

/((?s)b.)c(?!.)/
    a\nb\nc\n
 0: b\x0ac
 1: b\x0a
    a\nb\nc\n
 0: b\x0ac
 1: b\x0a

/^b/

/()^b/
\= Expect no match
    a\nb\nc\n
No match
    a\nb\nc\n
No match

/((?m)^b)/
    a\nb\nc\n
 0: b
 1: b

/(x)?(?(1)a|b)/
\= Expect no match
    a
No match
    a
No match

/(x)?(?(1)b|a)/
    a
 0: a

/()?(?(1)b|a)/
    a
 0: a

/()(?(1)b|a)/

/()?(?(1)a|b)/
    a
 0: a
 1: 

/^(\()?blah(?(1)(\)))$/
    (blah)
 0: (blah)
 1: (
 2: )
    blah
 0: blah
\= Expect no match
    a
No match
    blah)
No match
    (blah
No match

/^(\(+)?blah(?(1)(\)))$/
    (blah)
 0: (blah)
 1: (
 2: )
    blah
 0: blah
\= Expect no match
    blah)
No match
    (blah
No match

/(?(?!a)a|b)/

/(?(?!a)b|a)/
    a
 0: a

/(?(?=a)b|a)/
\= Expect no match
    a
No match
    a
No match

/(?(?=a)a|b)/
    a
 0: a

/(?=(a+?))(\1ab)/
    aaab
 0: aab
 1: a
 2: aab

/^(?=(a+?))\1ab/

/(\w+:)+/
    one:
 0: one:
 1: one:

/$(?<=^(a))/
    a
 0: 
 1: a

/(?=(a+?))(\1ab)/
    aaab
 0: aab
 1: a
 2: aab

/^(?=(a+?))\1ab/
\= Expect no match
    aaab
No match
    aaab
No match

/([\w:]+::)?(\w+)$/
    abcd
 0: abcd
 1: <unset>
 2: abcd
    xy:z:::abcd
 0: xy:z:::abcd
 1: xy:z:::
 2: abcd

/^[^bcd]*(c+)/
    aexycd
 0: aexyc
 1: c

/(a*)b+/
    caab
 0: aab
 1: aa

/([\w:]+::)?(\w+)$/
    abcd
 0: abcd
 1: <unset>
 2: abcd
    xy:z:::abcd
 0: xy:z:::abcd
 1: xy:z:::
 2: abcd
\= Expect no match
    abcd:
No match
    abcd:
No match

/^[^bcd]*(c+)/
    aexycd
 0: aexyc
 1: c

/(>a+)ab/

/(?>a+)b/
    aaab
 0: aaab

/([[:]+)/
    a:[b]:
 0: :[
 1: :[

/([[=]+)/
    a=[b]=
 0: =[
 1: =[

/([[.]+)/
    a.[b].
 0: .[
 1: .[

/((?>a+)b)/
    aaab
 0: aaab
 1: aaab

/(?>(a+))b/
    aaab
 0: aaab
 1: aaa

/((?>[^()]+)|\([^()]*\))+/
    ((abc(ade)ufh()()x
 0: abc(ade)ufh()()x
 1: x

/a\Z/
\= Expect no match
    aaab
No match
    a\nb\n
No match

/b\Z/
    a\nb\n
 0: b

/b\z/

/b\Z/
    a\nb
 0: b

/b\z/
    a\nb
 0: b
    
/^(?>(?(1)\.|())[^\W_](?>[a-z0-9-]*[^\W_])?)+$/
    a
 0: a
 1: 
    abc
 0: abc
 1: 
    a-b
 0: a-b
 1: 
    0-9 
 0: 0-9
 1: 
    a.b
 0: a.b
 1: 
    5.6.7  
 0: 5.6.7
 1: 
    the.quick.brown.fox
 0: the.quick.brown.fox
 1: 
    a100.b200.300c  
 0: a100.b200.300c
 1: 
    12-ab.1245 
 0: 12-ab.1245
 1: 
\= Expect no match
    \
No match
    .a
No match
    -a
No match
    a-
No match
    a.  
No match
    a_b 
No match
    a.-
No match
    a..  
No match
    ab..bc 
No match
    the.quick.brown.fox-
No match
    the.quick.brown.fox.
No match
    the.quick.brown.fox_
No match
    the.quick.brown.fox+       
No match

/(?>.*)(?<=(abcd|wxyz))/
    alphabetabcd
 0: alphabetabcd
 1: abcd
    endingwxyz
 0: endingwxyz
 1: wxyz
\= Expect no match
    a rather long string that doesn't end with one of them
No match

/word (?>(?:(?!otherword)[a-zA-Z0-9]+ ){0,30})otherword/
    word cat dog elephant mussel cow horse canary baboon snake shark otherword
 0: word cat dog elephant mussel cow horse canary baboon snake shark otherword
\= Expect no match
    word cat dog elephant mussel cow horse canary baboon snake shark
No match
  
/word (?>[a-zA-Z0-9]+ ){0,30}otherword/
\= Expect no match
    word cat dog elephant mussel cow horse canary baboon snake shark the quick brown fox and the lazy dog and several other words getting close to thirty by now I hope
No match

/(?<=\d{3}(?!999))foo/
    999foo
 0: foo
    123999foo 
 0: foo
\= Expect no match
    123abcfoo
No match
    
/(?<=(?!...999)\d{3})foo/
    999foo
 0: foo
    123999foo 
 0: foo
\= Expect no match
    123abcfoo
No match

/(?<=\d{3}(?!999)...)foo/
    123abcfoo
 0: foo
    123456foo 
 0: foo
\= Expect no match
    123999foo  
No match
    
/(?<=\d{3}...)(?<!999)foo/
    123abcfoo   
 0: foo
    123456foo 
 0: foo
\= Expect no match
    123999foo  
No match

/<a[\s]+href[\s]*=[\s]*          # find <a href=
 ([\"\'])?                       # find single or double quote
 (?(1) (.*?)\1 | ([^\s]+))       # if quote found, match up to next matching
                                 # quote, otherwise match up to next space
/isx
    <a href=abcd xyz
 0: <a href=abcd
 1: <unset>
 2: <unset>
 3: abcd
    <a href=\"abcd xyz pqr\" cats
 0: <a href="abcd xyz pqr"
 1: "
 2: abcd xyz pqr
    <a href=\'abcd xyz pqr\' cats
 0: <a href='abcd xyz pqr'
 1: '
 2: abcd xyz pqr

/<a\s+href\s*=\s*                # find <a href=
 (["'])?                         # find single or double quote
 (?(1) (.*?)\1 | (\S+))          # if quote found, match up to next matching
                                 # quote, otherwise match up to next space
/isx
    <a href=abcd xyz
 0: <a href=abcd
 1: <unset>
 2: <unset>
 3: abcd
    <a href=\"abcd xyz pqr\" cats
 0: <a href="abcd xyz pqr"
 1: "
 2: abcd xyz pqr
    <a href       =       \'abcd xyz pqr\' cats
 0: <a href       =       'abcd xyz pqr'
 1: '
 2: abcd xyz pqr

/<a\s+href(?>\s*)=(?>\s*)        # find <a href=
 (["'])?                         # find single or double quote
 (?(1) (.*?)\1 | (\S+))          # if quote found, match up to next matching
                                 # quote, otherwise match up to next space
/isx
    <a href=abcd xyz
 0: <a href=abcd
 1: <unset>
 2: <unset>
 3: abcd
    <a href=\"abcd xyz pqr\" cats
 0: <a href="abcd xyz pqr"
 1: "
 2: abcd xyz pqr
    <a href       =       \'abcd xyz pqr\' cats
 0: <a href       =       'abcd xyz pqr'
 1: '
 2: abcd xyz pqr

/(Z()|A)*/
    ZABCDEFG
 0: ZA
 1: A
 2: 

/(Z(())|A)*/
    ZABCDEFG
 0: ZA
 1: A
 2: 
 3: 

/((?>Z)+|A)*/
    ZABCDEFG
 0: ZA
 1: A

/((?>)+|A)*/
    ZABCDEFG
 0: 
 1: 

/a*/g
    abbab
 0: a
 0: 
 0: 
 0: a
 0: 
 0: 

/[[:space:]]+/
    > \x09\x0a\x0c\x0d\x0b<
 0:  \x09\x0a\x0c\x0d\x0b
     
/[[:blank:]]+/
    > \x09\x0a\x0c\x0d\x0b<
 0:  \x09
     
/[\s]+/
    > \x09\x0a\x0c\x0d\x0b<
 0:  \x09\x0a\x0c\x0d\x0b
     
/\s+/
    > \x09\x0a\x0c\x0d\x0b<
 0:  \x09\x0a\x0c\x0d\x0b
     
/ab/x
    ab
 0: ab

/(?!\A)x/m
    a\nxb\n
 0: x

/(?!^)x/m
\= Expect no match
    a\nxb\n
No match

/abc\Qabc\Eabc/
    abcabcabc
 0: abcabcabc
    
/abc\Q(*+|\Eabc/
    abc(*+|abc 
 0: abc(*+|abc

/   abc\Q abc\Eabc/x
    abc abcabc
 0: abc abcabc
\= Expect no match
    abcabcabc  
No match
    
/abc#comment
    \Q#not comment
    literal\E/x
    abc#not comment\n    literal     
 0: abc#not comment\x0a    literal

/abc#comment
    \Q#not comment
    literal/x
    abc#not comment\n    literal     
 0: abc#not comment\x0a    literal

/abc#comment
    \Q#not comment
    literal\E #more comment
    /x
    abc#not comment\n    literal     
 0: abc#not comment\x0a    literal

/abc#comment
    \Q#not comment
    literal\E #more comment/x
    abc#not comment\n    literal     
 0: abc#not comment\x0a    literal

/\Qabc\$xyz\E/
    abc\\\$xyz
 0: abc\$xyz

/\Qabc\E\$\Qxyz\E/
    abc\$xyz
 0: abc$xyz

/\Gabc/
    abc
 0: abc
\= Expect no match
    xyzabc  
No match

/\Gabc./g
    abc1abc2xyzabc3
 0: abc1
 0: abc2

/abc./g
    abc1abc2xyzabc3 
 0: abc1
 0: abc2
 0: abc3

/a(?x: b c )d/
    XabcdY
 0: abcd
\= Expect no match 
    Xa b c d Y 
No match

/((?x)x y z | a b c)/
    XabcY
 0: abc
 1: abc
    AxyzB 
 0: xyz
 1: xyz

/(?i)AB(?-i)C/
    XabCY
 0: abC
\= Expect no match
    XabcY  
No match

/((?i)AB(?-i)C|D)E/
    abCE
 0: abCE
 1: abC
    DE
 0: DE
 1: D
\= Expect no match
    abcE
No match
    abCe  
No match
    dE
No match
    De    
No match

/(.*)\d+\1/
    abc123abc
 0: abc123abc
 1: abc
    abc123bc 
 0: bc123bc
 1: bc

/(.*)\d+\1/s
    abc123abc
 0: abc123abc
 1: abc
    abc123bc 
 0: bc123bc
 1: bc
    
/((.*))\d+\1/
    abc123abc
 0: abc123abc
 1: abc
 2: abc
    abc123bc  
 0: bc123bc
 1: bc
 2: bc

# This tests for an IPv6 address in the form where it can have up to
# eight components, one and only one of which is empty. This must be
# an internal component. 

/^(?!:)                       # colon disallowed at start
  (?:                         # start of item
    (?: [0-9a-f]{1,4} |       # 1-4 hex digits or
    (?(1)0 | () ) )           # if null previously matched, fail; else null
    :                         # followed by colon
  ){1,7}                      # end item; 1-7 of them required               
  [0-9a-f]{1,4} $             # final hex number at end of string
  (?(1)|.)                    # check that there was an empty component
  /ix
    a123::a123
 0: a123::a123
 1: 
    a123:b342::abcd
 0: a123:b342::abcd
 1: 
    a123:b342::324e:abcd
 0: a123:b342::324e:abcd
 1: 
    a123:ddde:b342::324e:abcd
 0: a123:ddde:b342::324e:abcd
 1: 
    a123:ddde:b342::324e:dcba:abcd
 0: a123:ddde:b342::324e:dcba:abcd
 1: 
    a123:ddde:9999:b342::324e:dcba:abcd
 0: a123:ddde:9999:b342::324e:dcba:abcd
 1: 
\= Expect no match
    1:2:3:4:5:6:7:8
No match
    a123:bce:ddde:9999:b342::324e:dcba:abcd
No match
    a123::9999:b342::324e:dcba:abcd
No match
    abcde:2:3:4:5:6:7:8
No match
    ::1
No match
    abcd:fee0:123::   
No match
    :1
No match
    1:  
No match

/[z\Qa-d]\E]/
    z
 0: z
    a
 0: a
    -
 0: -
    d
 0: d
    ] 
 0: ]
\= Expect no match
    b     
No match

/(a+)*b/
\= Expect no match
    aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa 
No match
    
/(?i)reg(?:ul(?:[a�]|ae)r|ex)/
    REGular
 0: REGular
    regulaer
 0: regulaer
    Regex  
 0: Regex
    regul�r 
 0: regul\xe4r

/����[�-��-�]+/
    �����
 0: \xc5\xe6\xe5\xe4\xe0
    �����
 0: \xc5\xe6\xe5\xe4\xff
    �����
 0: \xc5\xe6\xe5\xe4\xc0
    �����
 0: \xc5\xe6\xe5\xe4\xdf

/(?<=Z)X./
  \x84XAZXB
 0: XB

/ab cd (?x) de fg/
    ab cd defg
 0: ab cd defg

/ab cd(?x) de fg/
    ab cddefg
 0: ab cddefg
\= Expect no match 
    abcddefg
No match

/(?<![^f]oo)(bar)/
    foobarX 
 0: bar
 1: bar
\= Expect no match 
    boobarX
No match

/(?<![^f])X/
    offX
 0: X
\= Expect no match
    onyX  
No match

/(?<=[^f])X/
    onyX
 0: X
\= Expect no match
    offX 
No match

/^/gm
    a\nb\nc\n
 0: 
 0: 
 0: 
    \ 
 0: 
    
/(?<=C\n)^/gm
    A\nC\nC\n 
 0: 

/(?:(?(1)a|b)(X))+/
    bXaX
 0: bXaX
 1: X

/(?:(?(1)\1a|b)(X|Y))+/
    bXXaYYaY
 0: bXXaYYaY
 1: Y
    bXYaXXaX  
 0: bX
 1: X

/()()()()()()()()()(?:(?(10)\10a|b)(X|Y))+/
    bXXaYYaY
 0: bX
 1: 
 2: 
 3: 
 4: 
 5: 
 6: 
 7: 
 8: 
 9: 
10: X

/[[,abc,]+]/
    abc]
 0: abc]
    a,b]
 0: a,b]
    [a,b,c]  
 0: [a,b,c]

/(?-x: )/x
    A\x20B
 0:  
    
/(?x)(?-x: \s*#\s*)/
    A # B
 0:  # 
\= Expect no match
    #  
No match
    A s#s B
No match

/(?x-is)(?:(?-ixs) \s*#\s*) include/
    A #include
 0:  #include
\= Expect no match
    A#include  
No match
    A #Include
No match

/a*b*\w/
    aaabbbb
 0: aaabbbb
    aaaa
 0: aaaa
    a
 0: a

/a*b?\w/
    aaabbbb
 0: aaabb
    aaaa
 0: aaaa
    a
 0: a

/a*b{0,4}\w/
    aaabbbb
 0: aaabbbb
    aaaa
 0: aaaa
    a
 0: a

/a*b{0,}\w/
    aaabbbb
 0: aaabbbb
    aaaa
 0: aaaa
    a
 0: a
    
/a*\d*\w/
    0a
 0: 0a
    a 
 0: a
    
/a*b *\w/x
    a 
 0: a

/a*b#comment
  *\w/x
    a 
 0: a

/a* b *\w/x
    a 
 0: a

/^\w+=.*(\\\n.*)*/
    abc=xyz\\\npqr
 0: abc=xyz\

/(?=(\w+))\1:/
    abcd:
 0: abcd:
 1: abcd

/^(?=(\w+))\1:/
    abcd:
 0: abcd:
 1: abcd

/^\Eabc/
    abc
 0: abc
    
/^[\Eabc]/
    a
 0: a
\= Expect no match 
    E 
No match
    
/^[a-\Ec]/
    b
 0: b
\= Expect no match
    -
No match
    E    
No match

/^[a\E\E-\Ec]/
    b
 0: b
\= Expect no match
    -
No match
    E    
No match

/^[\E\Qa\E-\Qz\E]+/
    b
 0: b
\= Expect no match
    -  
No match
    
/^[a\Q]bc\E]/
    a
 0: a
    ]
 0: ]
    c
 0: c
    
/^[a-\Q\E]/
    a
 0: a
    -     
 0: -

/^(a()*)*/
    aaaa
 0: aaaa
 1: a
 2: 

/^(?:a(?:(?:))*)*/
    aaaa
 0: aaaa

/^(a()+)+/
    aaaa
 0: aaaa
 1: a
 2: 

/^(?:a(?:(?:))+)+/
    aaaa
 0: aaaa

/(a){0,3}(?(1)b|(c|))*D/
    abbD
 0: abbD
 1: a
    ccccD
 0: ccccD
 1: <unset>
 2: 
    D  
 0: D
 1: <unset>
 2: 

/(a|)*\d/
  aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa4
 0: aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa4
 1: 
\= Expect no match
  aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
No match

/(?>a|)*\d/
  aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa4
 0: aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa4
\= Expect no match
  aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
No match

/(?:a|)*\d/
  aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa4
 0: aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa4
\= Expect no match
  aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
No match

/\Z/g
  abc\n
 0: 
 0: 
  
/^(?s)(?>.*)(?<!\n)/
  abc
 0: abc
\= Expect no match
  abc\n  
No match

/^(?![^\n]*\n\z)/
  abc
 0: 
\= Expect no match
  abc\n 
No match
  
/\z(?<!\n)/
  abc
 0: 
\= Expect no match
  abc\n  
No match

/(.*(.)?)*/
    abcd
 0: abcd
 1: 

/( (A | (?(1)0|) )*   )/x
    abcd
 0: 
 1: 
 2: 

/( ( (?(1)0|) )*   )/x
    abcd
 0: 
 1: 
 2: 

/(  (?(1)0|)*   )/x
    abcd
 0: 
 1: 

/[[:abcd:xyz]]/
    a]
 0: a]
    :] 
 0: :]
    
/[abc[:x\]pqr]/
    a
 0: a
    [
 0: [
    :
 0: :
    ]
 0: ]
    p    
 0: p

/.*[op][xyz]/
\= Expect no match
    fooabcfoo
No match

/(?(?=.*b)b|^)/
   adc
 0: 
   abc 
 0: b

/(?(?=^.*b)b|^)/
   adc
 0: 
\= Expect no match
   abc 
No match

/(?(?=.*b)b|^)*/
   adc
 0: 
   abc 
 0: 

/(?(?=.*b)b|^)+/
   adc
 0: 
   abc 
 0: b

/(?(?=b).*b|^d)/
    abc
 0: b

/(?(?=.*b).*b|^d)/
    abc
 0: ab

/^%((?(?=[a])[^%])|b)*%$/
    %ab%
 0: %ab%
 1: 

/(?i)a(?-i)b|c/
    XabX
 0: ab
    XAbX
 0: Ab
    CcC 
 0: c
\= Expect no match
    XABX   
No match

/[\x00-\xff\s]+/
    \x0a\x0b\x0c\x0d
 0: \x0a\x0b\x0c\x0d

/(abc)\1/i
\= Expect no match
   abc
No match

/(abc)\1/
\= Expect no match
   abc
No match

/[^a]*/i
    12abc
 0: 12
    12ABC
 0: 12

/[^a]*+/i
    12abc
 0: 12
    12ABC
 0: 12

/[^a]*?X/i
\= Expect no match
    12abc
No match
    12ABC
No match
    
/[^a]+?X/i
\= Expect no match
    12abc
No match
    12ABC
No match

/[^a]?X/i
    12aXbcX
 0: X
    12AXBCX
 0: X
    BCX 
 0: CX

/[^a]??X/i
    12aXbcX
 0: X
    12AXBCX
 0: X
    BCX
 0: CX
    
/[^a]?+X/i
    12aXbcX
 0: cX
    12AXBCX
 0: CX
    BCX 
 0: CX

/[^a]{2,3}/i
    abcdef
 0: bcd
    ABCDEF  
 0: BCD

/[^a]{2,3}?/i
    abcdef
 0: bc
    ABCDEF  
 0: BC

/[^a]{2,3}+/i
    abcdef
 0: bcd
    ABCDEF  
 0: BCD

/((a|)+)+Z/
    Z
 0: Z
 1: 
 2: 

/(a)b|(a)c/
    ac
 0: ac
 1: <unset>
 2: a

/(?>(a))b|(a)c/
    ac
 0: ac
 1: <unset>
 2: a

/(?=(a))ab|(a)c/
    ac
 0: ac
 1: <unset>
 2: a

/((?>(a))b|(a)c)/
    ac
 0: ac
 1: ac
 2: <unset>
 3: a

/((?>(a))b|(a)c)++/
    ac
 0: ac
 1: ac
 2: <unset>
 3: a

/(?:(?>(a))b|(a)c)++/
    ac
 0: ac
 1: <unset>
 2: a

/(?=(?>(a))b|(a)c)(..)/
    ac
 0: ac
 1: <unset>
 2: a
 3: ac

/(?>(?>(a))b|(a)c)/
    ac
 0: ac
 1: <unset>
 2: a

/(?:(?>([ab])))+a=/aftertext
    =ba=
 0: ba=
 0+ 
 1: b

/(?>([ab]))+a=/aftertext
    =ba=
 0: ba=
 0+ 
 1: b

/((?>(a+)b)+(aabab))/
    aaaabaaabaabab
 0: aaaabaaabaabab
 1: aaaabaaabaabab
 2: aaa
 3: aabab

/(?>a+|ab)+?c/
\= Expect no match
    aabc
No match

/(?>a+|ab)+c/
\= Expect no match
    aabc
No match

/(?:a+|ab)+c/
    aabc
 0: aabc

/(?(?=(a))a)/
    a
 0: a
 1: a

/(?(?=(a))a)(b)/
    ab
 0: ab
 1: a
 2: b

/^(?:a|ab)++c/
\= Expect no match
    aaaabc
No match

/^(?>a|ab)++c/
\= Expect no match
    aaaabc
No match

/^(?:a|ab)+c/
    aaaabc
 0: aaaabc

/(?=abc){3}abc/aftertext
    abcabcabc
 0: abc
 0+ abcabc
\= Expect no match
    xyz  
No match
    
/(?=abc)+abc/aftertext
    abcabcabc
 0: abc
 0+ abcabc
\= Expect no match
    xyz  
No match
    
/(?=abc)++abc/aftertext
    abcabcabc
 0: abc
 0+ abcabc
\= Expect no match
    xyz  
No match
    
/(?=abc){0}xyz/
    xyz 
 0: xyz

/(?=abc){1}xyz/
\= Expect no match
    xyz 
No match
    
/(?=(a))?./
    ab
 0: a
 1: a
    bc
 0: b
      
/(?=(a))??./
    ab
 0: a
    bc
 0: b

/^(?=(?1))?[az]([abc])d/
    abd 
 0: abd
 1: b
    zcdxx 
 0: zcd
 1: c

/^(?!a){0}\w+/
    aaaaa
 0: aaaaa

/(?<=(abc))?xyz/
    abcxyz
 0: xyz
 1: abc
    pqrxyz 
 0: xyz

/^[\g<a>]+/
    ggg<<<aaa>>>
 0: ggg<<<aaa>>>
\= Expect no match
    \\ga  
No match
    
/^[\ga]+/
    gggagagaxyz 
 0: gggagaga
    
/^[:a[:digit:]]+/
    aaaa444:::Z 
 0: aaaa444:::

/^[:a[:digit:]:b]+/
    aaaa444:::bbbZ 
 0: aaaa444:::bbb

/[:a]xxx[b:]/
     :xxx:
 0: :xxx:
     
/(?<=a{2})b/i
    xaabc
 0: b
\= Expect no match
    xabc  
No match

/(?<!a{2})b/i
    xabc
 0: b
\= Expect no match
    xaabc  
No match

/(?<=a\h)c/
    xa c
 0: c
    
/(?<=[^a]{2})b/
    axxbc
 0: b
    aAAbc 
 0: b
\= Expect no match
    xaabc    
No match

/(?<=[^a]{2})b/i
    axxbc  
 0: b
\= Expect no match
    aAAbc 
No match
    xaabc    
No match

/(?<=a\H)c/
    abc
 0: c

/(?<=a\V)c/
    abc
 0: c
    
/(?<=a\v)c/
    a\nc
 0: c

/(?(?=c)c|d)++Y/
    XcccddYX
 0: cccddY

/(?(?=c)c|d)*+Y/
    XcccddYX
 0: cccddY

/^(a{2,3}){2,}+a/
    aaaaaaa
 0: aaaaaaa
 1: aaa
\= Expect no match
    aaaaaa
No match
    aaaaaaaaa 
No match

/^(a{2,3})++a/
\= Expect no match
    aaaaaa
No match

/^(a{2,3})*+a/
\= Expect no match
    aaaaaa
No match

/\H\h\V\v/
    X X\x0a
 0: X X\x0a
    X\x09X\x0b
 0: X\x09X\x0b
\= Expect no match
    \xa0 X\x0a   
No match
    
/\H*\h+\V?\v{3,4}/
    \x09\x20\xa0X\x0a\x0b\x0c\x0d\x0a
 0: \x09 \xa0X\x0a\x0b\x0c\x0d
    \x09\x20\xa0\x0a\x0b\x0c\x0d\x0a
 0: \x09 \xa0\x0a\x0b\x0c\x0d
    \x09\x20\xa0\x0a\x0b\x0c
 0: \x09 \xa0\x0a\x0b\x0c
\= Expect no match 
    \x09\x20\xa0\x0a\x0b
No match
     
/\H{3,4}/
    XY  ABCDE
 0: ABCD
    XY  PQR ST 
 0: PQR
    
/.\h{3,4}./
    XY  AB    PQRS
 0: B    P

/\h*X\h?\H+Y\H?Z/
    >XNNNYZ
 0: XNNNYZ
    >  X NYQZ
 0:   X NYQZ
\= Expect no match
    >XYZ   
No match
    >  X NY Z
No match

/\v*X\v?Y\v+Z\V*\x0a\V+\x0b\V{2,3}\x0c/
    >XY\x0aZ\x0aA\x0bNN\x0c
 0: XY\x0aZ\x0aA\x0bNN\x0c
    >\x0a\x0dX\x0aY\x0a\x0bZZZ\x0aAAA\x0bNNN\x0c
 0: \x0a\x0dX\x0aY\x0a\x0bZZZ\x0aAAA\x0bNNN\x0c

/(foo)\Kbar/
    foobar
 0: bar
 1: foo
   
/(foo)(\Kbar|baz)/
    foobar
 0: bar
 1: foo
 2: bar
    foobaz 
 0: foobaz
 1: foo
 2: baz

/(foo\Kbar)baz/
    foobarbaz
 0: barbaz
 1: foobar

/abc\K|def\K/g,aftertext
    Xabcdefghi
 0: 
 0+ defghi
 0: 
 0+ ghi

/ab\Kc|de\Kf/g,aftertext
    Xabcdefghi
 0: c
 0+ defghi
 0: f
 0+ ghi
    
/(?=C)/g,aftertext
    ABCDECBA
 0: 
 0+ CDECBA
 0: 
 0+ CBA
    
/^abc\K/aftertext
    abcdef
 0: 
 0+ def
\= Expect no match
    defabcxyz   
No match

/^(a(b))\1\g1\g{1}\g-1\g{-1}\g{-2}Z/
    ababababbbabZXXXX
 0: ababababbbabZ
 1: ab
 2: b

/(?<A>tom|bon)-\g{A}/
    tom-tom
 0: tom-tom
 1: tom
    bon-bon 
 0: bon-bon
 1: bon
    
/(^(a|b\g{-1}))/
\= Expect no match
    bacxxx
No match

/(?|(abc)|(xyz))\1/
    abcabc
 0: abcabc
 1: abc
    xyzxyz 
 0: xyzxyz
 1: xyz
\= Expect no match
    abcxyz
No match
    xyzabc   
No match
    
/(?|(abc)|(xyz))(?1)/
    abcabc
 0: abcabc
 1: abc
    xyzabc 
 0: xyzabc
 1: xyz
\= Expect no match 
    xyzxyz 
No match
 
/^X(?5)(a)(?|(b)|(q))(c)(d)(Y)/
    XYabcdY
 0: XYabcdY
 1: a
 2: b
 3: c
 4: d
 5: Y

/^X(?7)(a)(?|(b|(r)(s))|(q))(c)(d)(Y)/
    XYabcdY
 0: XYabcdY
 1: a
 2: b
 3: <unset>
 4: <unset>
 5: c
 6: d
 7: Y

/^X(?7)(a)(?|(b|(?|(r)|(t))(s))|(q))(c)(d)(Y)/
    XYabcdY
 0: XYabcdY
 1: a
 2: b
 3: <unset>
 4: <unset>
 5: c
 6: d
 7: Y

/(?'abc'\w+):\k<abc>{2}/
    a:aaxyz
 0: a:aa
 1: a
    ab:ababxyz
 0: ab:abab
 1: ab
\= Expect no match
    a:axyz
No match
    ab:abxyz
No match

/(?'abc'\w+):\g{abc}{2}/
    a:aaxyz
 0: a:aa
 1: a
    ab:ababxyz
 0: ab:abab
 1: ab
\= Expect no match
    a:axyz
No match
    ab:abxyz
No match

/^(?<ab>a)? (?(<ab>)b|c) (?('ab')d|e)/x
    abd
 0: abd
 1: a
    ce
 0: ce

/^(a.)\g-1Z/
    aXaXZ
 0: aXaXZ
 1: aX

/^(a.)\g{-1}Z/
    aXaXZ
 0: aXaXZ
 1: aX

/^(?(DEFINE) (?<A> a) (?<B> b) )  (?&A) (?&B) /x
    abcd
 0: ab

/(?<all>(?:(?:a(?&all))|(b))(c?))/
    aabc
 0: aabc
 1: aabc
 2: <unset>
 3: 
    
/(a(b)|(c))(?1)/
    abc
 0: abc
 1: ab
 2: b
    cab 
 0: cab
 1: c
 2: <unset>
 3: c

/(?1)(a(b)|(c))/
    abc
 0: abc
 1: c
 2: <unset>
 3: c
    cab 
 0: cab
 1: ab
 2: b

/(?<NAME>(?&NAME_PAT))\s+(?<ADDR>(?&ADDRESS_PAT))
  (?(DEFINE)
  (?<NAME_PAT>[a-z]+)
  (?<ADDRESS_PAT>\d+)
  )/x
    metcalfe 33
 0: metcalfe 33
 1: metcalfe
 2: 33

/(?(DEFINE)(?<byte>2[0-4]\d|25[0-5]|1\d\d|[1-9]?\d))\b(?&byte)(\.(?&byte)){3}/
    1.2.3.4
 0: 1.2.3.4
 1: <unset>
 2: .4
    131.111.10.206
 0: 131.111.10.206
 1: <unset>
 2: .206
    10.0.0.0
 0: 10.0.0.0
 1: <unset>
 2: .0
\= Expect no match
    10.6
No match
    455.3.4.5
No match

/\b(?&byte)(\.(?&byte)){3}(?(DEFINE)(?<byte>2[0-4]\d|25[0-5]|1\d\d|[1-9]?\d))/
    1.2.3.4
 0: 1.2.3.4
 1: .4
    131.111.10.206
 0: 131.111.10.206
 1: .206
    10.0.0.0
 0: 10.0.0.0
 1: .0
\= Expect no match
    10.6
No match
    455.3.4.5
No match

/^(\w++|\s++)*$/
    now is the time for all good men to come to the aid of the party
 0: now is the time for all good men to come to the aid of the party
 1: party
\= Expect no match
    this is not a line with only words and spaces!
No match

/(\d++)(\w)/
    12345a
 0: 12345a
 1: 12345
 2: a
\= Expect no match
    12345+
No match

/a++b/
    aaab
 0: aaab

/(a++b)/
    aaab
 0: aaab
 1: aaab

/(a++)b/
    aaab
 0: aaab
 1: aaa

/([^()]++|\([^()]*\))+/
    ((abc(ade)ufh()()x
 0: abc(ade)ufh()()x
 1: x

/\(([^()]++|\([^()]+\))+\)/
    (abc)
 0: (abc)
 1: abc
    (abc(def)xyz)
 0: (abc(def)xyz)
 1: xyz
\= Expect no match
    ((()aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
No match

/^([^()]|\((?1)*\))*$/
    abc
 0: abc
 1: c
    a(b)c
 0: a(b)c
 1: c
    a(b(c))d
 0: a(b(c))d
 1: d
\= Expect no match)
    a(b(c)d
No match

/^>abc>([^()]|\((?1)*\))*<xyz<$/
   >abc>123<xyz<
 0: >abc>123<xyz<
 1: 3
   >abc>1(2)3<xyz<
 0: >abc>1(2)3<xyz<
 1: 3
   >abc>(1(2)3)<xyz<
 0: >abc>(1(2)3)<xyz<
 1: (1(2)3)

/^(?:((.)(?1)\2|)|((.)(?3)\4|.))$/i
    1221
 0: 1221
 1: 1221
 2: 1
    Satanoscillatemymetallicsonatas
 0: Satanoscillatemymetallicsonatas
 1: <unset>
 2: <unset>
 3: Satanoscillatemymetallicsonatas
 4: S
    AmanaplanacanalPanama
 0: AmanaplanacanalPanama
 1: <unset>
 2: <unset>
 3: AmanaplanacanalPanama
 4: A
    AblewasIereIsawElba
 0: AblewasIereIsawElba
 1: <unset>
 2: <unset>
 3: AblewasIereIsawElba
 4: A
\= Expect no match
    Thequickbrownfox
No match

/^(\d+|\((?1)([+*-])(?1)\)|-(?1))$/
    12
 0: 12
 1: 12
    (((2+2)*-3)-7)
 0: (((2+2)*-3)-7)
 1: (((2+2)*-3)-7)
 2: -
    -12
 0: -12
 1: -12
\= Expect no match
    ((2+2)*-3)-7)
No match

/^(x(y|(?1){2})z)/
    xyz
 0: xyz
 1: xyz
 2: y
    xxyzxyzz
 0: xxyzxyzz
 1: xxyzxyzz
 2: xyzxyz
\= Expect no match
    xxyzz
No match
    xxyzxyzxyzz
No match

/((< (?: (?(R) \d++  | [^<>]*+) | (?2)) * >))/x
    <>
 0: <>
 1: <>
 2: <>
    <abcd>
 0: <abcd>
 1: <abcd>
 2: <abcd>
    <abc <123> hij>
 0: <abc <123> hij>
 1: <abc <123> hij>
 2: <abc <123> hij>
    <abc <def> hij>
 0: <def>
 1: <def>
 2: <def>
    <abc<>def>
 0: <abc<>def>
 1: <abc<>def>
 2: <abc<>def>
    <abc<>
 0: <>
 1: <>
 2: <>
\= Expect no match
    <abc
No match

/^a+(*FAIL)/
\= Expect no match
    aaaaaa
No match
    
/a+b?c+(*FAIL)/
\= Expect no match
    aaabccc
No match

/a+b?(*PRUNE)c+(*FAIL)/
\= Expect no match
    aaabccc
No match

/a+b?(*COMMIT)c+(*FAIL)/
\= Expect no match
    aaabccc
No match
    
/a+b?(*SKIP)c+(*FAIL)/
\= Expect no match
    aaabcccaaabccc
No match

/^(?:aaa(*THEN)\w{6}|bbb(*THEN)\w{5}|ccc(*THEN)\w{4}|\w{3})/
    aaaxxxxxx
 0: aaaxxxxxx
    aaa++++++ 
 0: aaa
    bbbxxxxx
 0: bbbxxxxx
    bbb+++++ 
 0: bbb
    cccxxxx
 0: cccxxxx
    ccc++++ 
 0: ccc
    dddddddd   
 0: ddd

/^(aaa(*THEN)\w{6}|bbb(*THEN)\w{5}|ccc(*THEN)\w{4}|\w{3})/
    aaaxxxxxx
 0: aaaxxxxxx
 1: aaaxxxxxx
    aaa++++++ 
 0: aaa
 1: aaa
    bbbxxxxx
 0: bbbxxxxx
 1: bbbxxxxx
    bbb+++++ 
 0: bbb
 1: bbb
    cccxxxx
 0: cccxxxx
 1: cccxxxx
    ccc++++ 
 0: ccc
 1: ccc
    dddddddd   
 0: ddd
 1: ddd

/a+b?(*THEN)c+(*FAIL)/
\= Expect no match
    aaabccc
No match

/(A (A|B(*ACCEPT)|C) D)(E)/x
    AB
 0: AB
 1: AB
 2: B
    ABX
 0: AB
 1: AB
 2: B
    AADE
 0: AADE
 1: AAD
 2: A
 3: E
    ACDE
 0: ACDE
 1: ACD
 2: C
 3: E
\= Expect no match
    AD 
No match
        
/^\W*+(?:((.)\W*+(?1)\W*+\2|)|((.)\W*+(?3)\W*+\4|\W*+.\W*+))\W*+$/i
    1221
 0: 1221
 1: 1221
 2: 1
    Satan, oscillate my metallic sonatas!
 0: Satan, oscillate my metallic sonatas!
 1: <unset>
 2: <unset>
 3: Satan, oscillate my metallic sonatas
 4: S
    A man, a plan, a canal: Panama!
 0: A man, a plan, a canal: Panama!
 1: <unset>
 2: <unset>
 3: A man, a plan, a canal: Panama
 4: A
    Able was I ere I saw Elba.
 0: Able was I ere I saw Elba.
 1: <unset>
 2: <unset>
 3: Able was I ere I saw Elba
 4: A
\= Expect no match
    The quick brown fox
No match

/^((.)(?1)\2|.)$/
    a
 0: a
 1: a
    aba
 0: aba
 1: aba
 2: a
    aabaa  
 0: aabaa
 1: aabaa
 2: a
    abcdcba 
 0: abcdcba
 1: abcdcba
 2: a
    pqaabaaqp  
 0: pqaabaaqp
 1: pqaabaaqp
 2: p
    ablewasiereisawelba
 0: ablewasiereisawelba
 1: ablewasiereisawelba
 2: a
\= Expect no match     
    rhubarb
No match
    the quick brown fox  
No match

/(a)(?<=b(?1))/
    baz
 0: a
 1: a
\= Expect no match
    caz  
No match
    
/(?<=b(?1))(a)/
    zbaaz
 0: a
 1: a
\= Expect no match
    aaa  
No match
    
/(?<X>a)(?<=b(?&X))/
    baz
 0: a
 1: a

/^(?|(abc)|(def))\1/
    abcabc
 0: abcabc
 1: abc
    defdef 
 0: defdef
 1: def
\= Expect no match
    abcdef
No match
    defabc   
No match
    
/^(?|(abc)|(def))(?1)/
    abcabc
 0: abcabc
 1: abc
    defabc
 0: defabc
 1: def
\= Expect no match
    defdef
No match
    abcdef    
No match

/(?:a(?<quote> (?<apostrophe>')|(?<realquote>")) |b(?<quote> (?<apostrophe>')|(?<realquote>")) ) (?('quote')[a-z]+|[0-9]+)/x,dupnames
    a\"aaaaa
 0: a"aaaaa
 1: "
 2: <unset>
 3: "
    b\"aaaaa 
 0: b"aaaaa
 1: <unset>
 2: <unset>
 3: <unset>
 4: "
 5: <unset>
 6: "
\= Expect no match 
    b\"11111
No match

/(?:(?1)|B)(A(*F)|C)/
    ABCD
 0: BC
 1: C
    CCD
 0: CC
 1: C
\= Expect no match
    CAD   
No match

/^(?:(?1)|B)(A(*F)|C)/
    CCD
 0: CC
 1: C
    BCD 
 0: BC
 1: C
\= Expect no match
    ABCD
No match
    CAD
No match
    BAD    
No match

/(?:(?1)|B)(A(*ACCEPT)XX|C)D/
    AAD
 0: AA
 1: A
    ACD
 0: ACD
 1: C
    BAD
 0: BA
 1: A
    BCD
 0: BCD
 1: C
    BAX  
 0: BA
 1: A
\= Expect no match
    ACX
No match
    ABC   
No match

/(?(DEFINE)(A))B(?1)C/
    BAC
 0: BAC

/(?(DEFINE)((A)\2))B(?1)C/
    BAAC
 0: BAAC

/(?<pn> \( ( [^()]++ | (?&pn) )* \) )/x
    (ab(cd)ef)
 0: (ab(cd)ef)
 1: (ab(cd)ef)
 2: ef

/^(?=a(*SKIP)b|ac)/
\= Expect no match
    ac
No match
    
/^(?=a(*PRUNE)b)/
    ab  
 0: 
\= Expect no match 
    ac
No match

/^(?=a(*ACCEPT)b)/
    ac
 0: 

/(?>a\Kb)/
    ab
 0: b

/((?>a\Kb))/
    ab
 0: b
 1: ab

/(a\Kb)/
    ab
 0: b
 1: ab
    
/^a\Kcz|ac/
    ac
 0: ac
    
/(?>a\Kbz|ab)/
    ab 
 0: ab

/^(?&t)(?(DEFINE)(?<t>a\Kb))$/
    ab
 0: b

/^([^()]|\((?1)*\))*$/
    a(b)c
 0: a(b)c
 1: c
    a(b(c)d)e 
 0: a(b(c)d)e
 1: e

/(?P<L1>(?P<L2>0)(?P>L1)|(?P>L2))/
    0
 0: 0
 1: 0
    00
 0: 00
 1: 00
 2: 0
    0000  
 0: 0000
 1: 0000
 2: 0

/(?P<L1>(?P<L2>0)|(?P>L2)(?P>L1))/
    0
 0: 0
 1: 0
 2: 0
    00
 0: 0
 1: 0
 2: 0
    0000  
 0: 0
 1: 0
 2: 0

# This one does fail, as expected, in Perl. It needs the complex item at the
# end of the pattern. A single letter instead of (B|D) makes it not fail, which
# I think is a Perl bug.

/A(*COMMIT)(B|D)/
\= Expect no match
    ACABX
No match

# Check the use of names for failure

/^(A(*PRUNE:A)B|C(*PRUNE:B)D)/mark
\= Expect no match
    AC
No match, mark = A
    CB    
No match, mark = B
    
/(*MARK:A)(*SKIP:B)(C|X)/mark
    C
 0: C
 1: C
MK: A
\= Expect no match
    D
No match, mark = A
     
/^(A(*THEN:A)B|C(*THEN:B)D)/mark
\= Expect no match
    CB    
No match, mark = B

/^(?:A(*THEN:A)B|C(*THEN:B)D)/mark
\= Expect no match
    CB    
No match, mark = B
    
/^(?>A(*THEN:A)B|C(*THEN:B)D)/mark
\= Expect no match
    CB    
No match, mark = B
    
# This should succeed, as the skip causes bump to offset 1 (the mark). Note
# that we have to have something complicated such as (B|Z) at the end because,
# for Perl, a simple character somehow causes an unwanted optimization to mess
# with the handling of backtracking verbs.

/A(*MARK:A)A+(*SKIP:A)(B|Z) | AC/x,mark
    AAAC
 0: AC
    
# Test skipping over a non-matching mark.

/A(*MARK:A)A+(*MARK:B)(*SKIP:A)(B|Z) | AC/x,mark
    AAAC
 0: AC
    
# Check shorthand for MARK.

/A(*:A)A+(*SKIP:A)(B|Z) | AC/x,mark
    AAAC
 0: AC

/(*:A)A+(*SKIP:A)(B|Z)/mark
\= Expect no match
    AAAC
No match, mark = A

# This should succeed, as a non-existent skip name disables the skip.

/A(*MARK:A)A+(*SKIP:B)(B|Z) | AC/x,mark
    AAAC
 0: AC

/A(*MARK:A)A+(*SKIP:B)(B|Z) | AC(*:B)/x,mark
    AAAC
 0: AC
MK: B

# COMMIT at the start of a pattern should act like an anchor. Again, however,
# we need the complication for Perl.

/(*COMMIT)(A|P)(B|P)(C|P)/
    ABCDEFG
 0: ABC
 1: A
 2: B
 3: C
\= Expect no match
    DEFGABC  
No match

# COMMIT inside an atomic group can't stop backtracking over the group.

/(\w+)(?>b(*COMMIT))\w{2}/
    abbb
 0: abbb
 1: a

/(\w+)b(*COMMIT)\w{2}/
\= Expect no match
    abbb
No match

# Check opening parens in comment when seeking forward reference.

/(?&t)(?#()(?(DEFINE)(?<t>a))/
    bac
 0: a

# COMMIT should override THEN.

/(?>(*COMMIT)(?>yes|no)(*THEN)(*F))?/
\= Expect no match
  yes
No match

/(?>(*COMMIT)(yes|no)(*THEN)(*F))?/
\= Expect no match
  yes
No match

/b?(*SKIP)c/
    bc
 0: bc
    abc
 0: bc
   
/(*SKIP)bc/
\= Expect no match
    a
No match

/(*SKIP)b/
\= Expect no match
    a 
No match

/(?P<abn>(?P=abn)xxx|)+/
    xxx
 0: 
 1: 

/(?i:([^b]))(?1)/
    aa
 0: aa
 1: a
    aA     
 0: aA
 1: a
\= Expect no match
    ab
No match
    aB
No match
    Ba
No match
    ba
No match

/^(?&t)*+(?(DEFINE)(?<t>a))\w$/
    aaaaaaX
 0: aaaaaaX
\= Expect no match 
    aaaaaa 
No match

/^(?&t)*(?(DEFINE)(?<t>a))\w$/
    aaaaaaX
 0: aaaaaaX
    aaaaaa 
 0: aaaaaa

/^(a)*+(\w)/
    aaaaX
 0: aaaaX
 1: a
 2: X
    YZ 
 0: Y
 1: <unset>
 2: Y
\= Expect no match 
    aaaa
No match

/^(?:a)*+(\w)/
    aaaaX
 0: aaaaX
 1: X
    YZ 
 0: Y
 1: Y
\= Expect no match 
    aaaa
No match

/^(a)++(\w)/
    aaaaX
 0: aaaaX
 1: a
 2: X
\= Expect no match 
    aaaa
No match
    YZ 
No match

/^(?:a)++(\w)/
    aaaaX
 0: aaaaX
 1: X
\= Expect no match 
    aaaa
No match
    YZ 
No match

/^(a)?+(\w)/
    aaaaX
 0: aa
 1: a
 2: a
    YZ 
 0: Y
 1: <unset>
 2: Y

/^(?:a)?+(\w)/
    aaaaX
 0: aa
 1: a
    YZ 
 0: Y
 1: Y

/^(a){2,}+(\w)/
    aaaaX
 0: aaaaX
 1: a
 2: X
\= Expect no match
    aaa
No match
    YZ 
No match

/^(?:a){2,}+(\w)/
    aaaaX
 0: aaaaX
 1: X
\= Expect no match
    aaa
No match
    YZ 
No match

/(a|)*(?1)b/
    b
 0: b
 1: 
    ab
 0: ab
 1: 
    aab  
 0: aab
 1: 

/(a)++(?1)b/
\= Expect no match
    ab 
No match
    aab
No match

/(a)*+(?1)b/
\= Expect no match
    ab
No match
    aab  
No match

/(?1)(?:(b)){0}/
    b
 0: b

/(foo ( \( ((?:(?> [^()]+ )|(?2))*) \) ) )/x
    foo(bar(baz)+baz(bop))
 0: foo(bar(baz)+baz(bop))
 1: foo(bar(baz)+baz(bop))
 2: (bar(baz)+baz(bop))
 3: bar(baz)+baz(bop)

/(A (A|B(*ACCEPT)|C) D)(E)/x
    AB
 0: AB
 1: AB
 2: B

/\A.*?(a|bc)/
    ba
 0: ba
 1: a

/\A.*?(?:a|bc)++/
    ba
 0: ba

/\A.*?(a|bc)++/
    ba
 0: ba
 1: a

/\A.*?(?:a|bc|d)/
    ba
 0: ba

/(?:(b))++/
    beetle
 0: b
 1: b

/(?(?=(a(*ACCEPT)z))a)/
    a
 0: a
 1: a

/^(a)(?1)+ab/
    aaaab
 0: aaaab
 1: a
    
/^(a)(?1)++ab/
\= Expect no match
    aaaab
No match

/^(?=a(*:M))aZ/mark
    aZbc
 0: aZ
MK: M

/^(?!(*:M)b)aZ/mark
    aZbc
 0: aZ

/(?(DEFINE)(a))?b(?1)/
    backgammon
 0: ba

/^\N+/
    abc\ndef
 0: abc
    
/^\N{1,}/
    abc\ndef 
 0: abc

/(?(R)a+|(?R)b)/
    aaaabcde
 0: aaaab

/(?(R)a+|((?R))b)/
    aaaabcde
 0: aaaab
 1: aaaa

/((?(R)a+|(?1)b))/
    aaaabcde
 0: aaaab
 1: aaaab

/((?(R1)a+|(?1)b))/
    aaaabcde
 0: aaaab
 1: aaaab
    
/((?(R)a|(?1)))*/
    aaa
 0: aaa
 1: a

/((?(R)a|(?1)))+/
    aaa 
 0: aaa
 1: a

/a(*:any 
name)/mark
    abc
 0: a
MK: any \x0aname
    
/(?>(?&t)c|(?&t))(?(DEFINE)(?<t>a|b(*PRUNE)c))/
    a
 0: a
    ba
 0: a
    bba 
 0: a
    
# Checking revised (*THEN) handling.

# Capture

/^.*? (a(*THEN)b) c/x
\= Expect no match
    aabc
No match

/^.*? (a(*THEN)b|(*F)) c/x
    aabc
 0: aabc
 1: ab

/^.*? ( (a(*THEN)b) | (*F) ) c/x
    aabc
 0: aabc
 1: ab
 2: ab

/^.*? ( (a(*THEN)b) ) c/x
\= Expect no match
    aabc
No match

# Non-capture

/^.*? (?:a(*THEN)b) c/x
\= Expect no match
    aabc
No match

/^.*? (?:a(*THEN)b|(*F)) c/x
    aabc
 0: aabc

/^.*? (?: (?:a(*THEN)b) | (*F) ) c/x
    aabc
 0: aabc

/^.*? (?: (?:a(*THEN)b) ) c/x
\= Expect no match
    aabc
No match

# Atomic

/^.*? (?>a(*THEN)b) c/x
\= Expect no match
    aabc
No match

/^.*? (?>a(*THEN)b|(*F)) c/x
    aabc
 0: aabc

/^.*? (?> (?>a(*THEN)b) | (*F) ) c/x
    aabc
 0: aabc

/^.*? (?> (?>a(*THEN)b) ) c/x
\= Expect no match
    aabc
No match

# Possessive capture

/^.*? (a(*THEN)b)++ c/x
\= Expect no match
    aabc
No match

/^.*? (a(*THEN)b|(*F))++ c/x
    aabc
 0: aabc
 1: ab

/^.*? ( (a(*THEN)b)++ | (*F) )++ c/x
    aabc
 0: aabc
 1: ab
 2: ab

/^.*? ( (a(*THEN)b)++ )++ c/x
\= Expect no match
    aabc
No match

# Possessive non-capture

/^.*? (?:a(*THEN)b)++ c/x
\= Expect no match
    aabc
No match

/^.*? (?:a(*THEN)b|(*F))++ c/x
    aabc
 0: aabc

/^.*? (?: (?:a(*THEN)b)++ | (*F) )++ c/x
    aabc
 0: aabc

/^.*? (?: (?:a(*THEN)b)++ )++ c/x
\= Expect no match
    aabc
No match
    
# Condition assertion

/^(?(?=a(*THEN)b)ab|ac)/
    ac
 0: ac
 
# Condition

/^.*?(?(?=a)a|b(*THEN)c)/
\= Expect no match
    ba
No match

/^.*?(?:(?(?=a)a|b(*THEN)c)|d)/
    ba
 0: ba

/^.*?(?(?=a)a(*THEN)b|c)/
\= Expect no match
    ac
No match

# Assertion

/^.*(?=a(*THEN)b)/
    aabc
 0: a

# --------------------------

/(?>a(*:m))/imsx,mark
    a
 0: a
MK: m

/(?>(a)(*:m))/imsx,mark
    a
 0: a
 1: a
MK: m

/(?<=a(*ACCEPT)b)c/
    xacd
 0: c

/(?<=(a(*ACCEPT)b))c/
    xacd
 0: c
 1: a

/(?<=(a(*COMMIT)b))c/
    xabcd
 0: c
 1: ab
\= Expect no match 
    xacd
No match
    
/(?<!a(*FAIL)b)c/
    xcd
 0: c
    acd 
 0: c

/(?<=a(*:N)b)c/mark
    xabcd
 0: c
MK: N
    
/(?<=a(*PRUNE)b)c/
    xabcd 
 0: c

/(?<=a(*SKIP)b)c/
    xabcd 
 0: c

/(?<=a(*THEN)b)c/
    xabcd 
 0: c

/(a)(?2){2}(.)/
    abcd
 0: abcd
 1: a
 2: d

/(*MARK:A)(*PRUNE:B)(C|X)/mark
    C
 0: C
 1: C
MK: B
\= Expect no match
    D 
No match, mark = B

/(*MARK:A)(*PRUNE:B)(C|X)/mark
    C
 0: C
 1: C
MK: B
\= Expect no match
    D 
No match, mark = B

/(*MARK:A)(*THEN:B)(C|X)/mark
    C
 0: C
 1: C
MK: B
\= Expect no match
    D 
No match, mark = B

/(*MARK:A)(*THEN:B)(C|X)/mark,no_start_optimize
    C
 0: C
 1: C
MK: B
\= Expect no match
    D 
No match, mark = B

/(*MARK:A)(*THEN:B)(C|X)/mark
    C
 0: C
 1: C
MK: B
\= Expect no match
    D 
No match, mark = B

# This should fail, as the skip causes a bump to offset 3 (the skip).

/A(*MARK:A)A+(*SKIP)(B|Z) | AC/x,mark
\= Expect no match
    AAAC
No match, mark = A

# Same 

/A(*MARK:A)A+(*MARK:B)(*SKIP:B)(B|Z) | AC/x,mark
\= Expect no match
    AAAC
No match, mark = B

/A(*:A)A+(*SKIP)(B|Z) | AC/x,mark
\= Expect no match
    AAAC
No match, mark = A

# This should fail, as a null name is the same as no name.

/A(*MARK:A)A+(*SKIP:)(B|Z) | AC/x,mark
\= Expect no match
    AAAC
No match, mark = A

# A check on what happens after hitting a mark and them bumping along to
# something that does not even start. Perl reports tags after the failures
# here, though it does not when the individual letters are made into something
# more complicated.

/A(*:A)B|XX(*:B)Y/mark
    AABC
 0: AB
MK: A
    XXYZ 
 0: XXY
MK: B
\= Expect no match
    XAQQ  
No match, mark = A
    XAQQXZZ  
No match, mark = A
    AXQQQ 
No match, mark = A
    AXXQQQ 
No match, mark = B
    
/^(A(*THEN:A)B|C(*THEN:B)D)/mark
    AB
 0: AB
 1: AB
MK: A
    CD
 0: CD
 1: CD
MK: B
\= Expect no match
    AC
No match, mark = A
    CB    
No match, mark = B
    
/^(A(*PRUNE:A)B|C(*PRUNE:B)D)/mark
    AB
 0: AB
 1: AB
MK: A
    CD
 0: CD
 1: CD
MK: B
\= Expect no match
    AC
No match, mark = A
    CB    
No match, mark = B
    
# An empty name does not pass back an empty string. It is the same as if no
# name were given.

/^(A(*PRUNE:)B|C(*PRUNE:B)D)/mark
    AB
 0: AB
 1: AB
    CD 
 0: CD
 1: CD
MK: B

# PRUNE goes to next bumpalong; COMMIT does not.
    
/A(*PRUNE:A)B/mark
    ACAB
 0: AB
MK: A

# Mark names can be duplicated.

/A(*:A)B|X(*:A)Y/mark
    AABC
 0: AB
MK: A
    XXYZ 
 0: XY
MK: A
    
/b(*:m)f|a(*:n)w/mark
    aw 
 0: aw
MK: n
\= Expect no match 
    abc
No match, mark = m

/b(*:m)f|aw/mark
    abaw
 0: aw
\= Expect no match 
    abc
No match, mark = m
    abax 
No match, mark = m

/A(*MARK:A)A+(*SKIP:B)(B|Z) | AAC/x,mark
    AAAC
 0: AAC

/(?=a(*MARK:A)b)..x/mark
    abxy
 0: abx
MK: A
\= Expect no match
    abpq  
No match

/(?=a(*MARK:A)b)..(*:Y)x/mark
    abxy
 0: abx
MK: Y
\= Expect no match
    abpq  
No match

/(?=a(*PRUNE:A)b)..x/mark
    abxy
 0: abx
MK: A
\= Expect no match
    abpq  
No match

/(?=a(*PRUNE:A)b)..(*:Y)x/mark
    abxy
 0: abx
MK: Y
\= Expect no match
    abpq  
No match

/(?=a(*THEN:A)b)..x/mark
    abxy
 0: abx
MK: A
\= Expect no match
    abpq  
No match

/(?=a(*THEN:A)b)..(*:Y)x/mark
    abxy
 0: abx
MK: Y
\= Expect no match
    abpq  
No match

/(another)?(\1?)test/
    hello world test
 0: test
 1: <unset>
 2: 

/(another)?(\1+)test/
\= Expect no match
    hello world test
No match

/(a(*COMMIT)b){0}a(?1)|aac/
    aac
 0: aac

/((?:a?)*)*c/
    aac   
 0: aac
 1: 

/((?>a?)*)*c/
    aac   
 0: aac
 1: 

/(?>.*?a)(?<=ba)/
    aba
 0: ba

/(?:.*?a)(?<=ba)/
    aba
 0: aba

/(?>.*?a)b/s
    aab
 0: ab

/(?>.*?a)b/
    aab
 0: ab

/(?>^a)b/s
\= Expect no match
    aab
No match

/(?>.*?)(?<=(abcd)|(wxyz))/
    alphabetabcd
 0: 
 1: abcd
    endingwxyz 
 0: 
 1: <unset>
 2: wxyz

/(?>.*)(?<=(abcd)|(wxyz))/
    alphabetabcd
 0: alphabetabcd
 1: abcd
    endingwxyz 
 0: endingwxyz
 1: <unset>
 2: wxyz

/(?>.*)foo/
\= Expect no match
    abcdfooxyz
No match
    
/(?>.*?)foo/
    abcdfooxyz
 0: foo

/(?:(a(*PRUNE)b)){0}(?:(?1)|ac)/
    ac
 0: ac
    
/(?:(a(*SKIP)b)){0}(?:(?1)|ac)/
    ac 
 0: ac

/(?<=(*SKIP)ac)a/
\= Expect no match
    aa
No match

/A(*MARK:A)A+(*SKIP:B)(B|Z) | AC/x,mark
    AAAC
 0: AC

/a(*SKIP:m)x|ac(*:n)(*SKIP:n)d|ac/mark
    acacd
 0: acd
MK: n

/A(*SKIP:m)x|A(*SKIP:n)x|AB/mark
    AB
 0: AB

/((*SKIP:r)d){0}a(*SKIP:m)x|ac(*:n)|ac/mark
    acacd
 0: ac
MK: n

# Tests that try to figure out how Perl works. My hypothesis is that the first
# verb that is backtracked onto is the one that acts. This seems to be the case
# almost all the time, but there is one exception that is perhaps a bug.

# This matches "aaaac"; each PRUNE advances one character until the subject no
# longer starts with 5 'a's.

/aaaaa(*PRUNE)b|a+c/
    aaaaaac
 0: aaaac

# Putting SKIP in front of PRUNE makes no difference, as it is never
# backtracked onto, whether or not it has a label.

/aaaaa(*SKIP)(*PRUNE)b|a+c/
    aaaaaac
 0: aaaac

/aaaaa(*SKIP:N)(*PRUNE)b|a+c/
    aaaaaac
 0: aaaac

/aaaa(*:N)a(*SKIP:N)(*PRUNE)b|a+c/
    aaaaaac
 0: aaaac

# Putting THEN in front makes no difference.
    
/aaaaa(*THEN)(*PRUNE)b|a+c/
    aaaaaac
 0: aaaac
 
# However, putting COMMIT in front of the prune changes it to "no match". I 
# think this is inconsistent and possibly a bug. For the moment, running this
# test is moved out of the Perl-compatible file. 

/aaaaa(*COMMIT)(*PRUNE)b|a+c/
    
# OK, lets play the same game again using SKIP instead of PRUNE.

# This matches "ac" because SKIP forces the next match to start on the
# sixth "a". 

/aaaaa(*SKIP)b|a+c/
    aaaaaac
 0: ac
 
# Putting PRUNE in front makes no difference. 

/aaaaa(*PRUNE)(*SKIP)b|a+c/
    aaaaaac
 0: ac

# Putting THEN in front makes no difference. 

/aaaaa(*THEN)(*SKIP)b|a+c/
    aaaaaac
 0: ac

# In this case, neither does COMMIT. This still matches "ac". 

/aaaaa(*COMMIT)(*SKIP)b|a+c/
    aaaaaac
 0: ac
    
# This gives "no match", as expected. 

/aaaaa(*COMMIT)b|a+c/
\= Expect no match
    aaaaaac
No match

# ---- Tests using THEN ----

# This matches "aaaaaac", as expected. 

/aaaaa(*THEN)b|a+c/
    aaaaaac
 0: aaaaaac

# Putting SKIP in front makes no difference. 

/aaaaa(*SKIP)(*THEN)b|a+c/
    aaaaaac
 0: aaaaaac
    
# Putting PRUNE in front makes no difference. 

/aaaaa(*PRUNE)(*THEN)b|a+c/
    aaaaaac
 0: aaaaaac
    
# Putting COMMIT in front makes no difference. 

/aaaaa(*COMMIT)(*THEN)b|a+c/
    aaaaaac
 0: aaaaaac
    
# End of "priority" tests  

/aaaaa(*:m)(*PRUNE:m)(*SKIP:m)m|a+/
    aaaaaa
 0: a

/aaaaa(*:m)(*MARK:m)(*PRUNE)(*SKIP:m)m|a+/
    aaaaaa
 0: a

/aaaaa(*:n)(*PRUNE:m)(*SKIP:m)m|a+/
    aaaaaa
 0: aaaa

/aaaaa(*:n)(*MARK:m)(*PRUNE)(*SKIP:m)m|a+/
    aaaaaa
 0: a

/a(*MARK:A)aa(*PRUNE:A)a(*SKIP:A)b|a+c/
    aaaac
 0: aac

/a(*MARK:A)aa(*MARK:A)a(*SKIP:A)b|a+c/
    aaaac
 0: ac

/aaa(*PRUNE:A)a(*SKIP:A)b|a+c/
    aaaac
 0: aac

/aaa(*MARK:A)a(*SKIP:A)b|a+c/
    aaaac
 0: ac

/a(*:m)a(*COMMIT)(*SKIP:m)b|a+c/mark
    aaaaaac
 0: ac

/.?(a|b(*THEN)c)/
    ba
 0: ba
 1: a

/(a(*COMMIT)b)c|abd/
    abc
 0: abc
 1: ab
\= Expect no match
    abd
No match

/(?=a(*COMMIT)b)abc|abd/
    abc
 0: abc
    abd
 0: abd

/(?>a(*COMMIT)b)c|abd/
    abc
 0: abc
    abd
 0: abd

/a(?=b(*COMMIT)c)[^d]|abd/
    abc
 0: ab
\= Expect no match
    abd
No match

/a(?=bc).|abd/
    abd
 0: abd
    abc 
 0: ab
    
/a(?>b(*COMMIT)c)d|abd/
\= Expect no match
    abceabd 
No match

/a(?>bc)d|abd/
    abceabd 
 0: abd

/(?>a(*COMMIT)b)c|abd/
    abd
 0: abd

/(?>a(*COMMIT)c)d|abd/
\= Expect no match
    abd
No match

/((?=a(*COMMIT)b)ab|ac){0}(?:(?1)|a(c))/
    ac 
 0: ac
 1: <unset>
 2: c
    
# These tests were formerly in test 2, but changes in PCRE and Perl have
# made them compatible. 
    
/^(a)?(?(1)a|b)+$/
\= Expect no match
    a
No match

/A(*PRUNE:A)A+(*SKIP:A)(B|Z) | AC/x,mark
\= Expect no match
    AAAC
No match, mark = A

/^((abc|abcx)(*THEN)y|abcd)/
    abcd
 0: abcd
 1: abcd
\= Expect no match 
    abcxy 
No match
    
/^((yes|no)(*THEN)(*F))?/
\= Expect no match
    yes
No match

/(A (.*)   C? (*THEN)  | A D) (*FAIL)/x
\= Expect no match
    AbcdCBefgBhiBqz
No match

/(A (.*)   C? (*THEN)  | A D) z/x
\= Expect no match
    AbcdCBefgBhiBqz
No match

/(A (.*)   C? (*THEN)  | A D) \s* (*FAIL)/x
\= Expect no match
    AbcdCBefgBhiBqz
No match

/(A (.*)   C? (*THEN)  | A D) \s* z/x
\= Expect no match
    AbcdCBefgBhiBqz
No match

/(A (.*)   (?:C|) (*THEN)  | A D) (*FAIL)/x
\= Expect no match
    AbcdCBefgBhiBqz
No match

/(A (.*)   (?:C|) (*THEN)  | A D) z/x
\= Expect no match
    AbcdCBefgBhiBqz
No match

/(A (.*)   C{0,6} (*THEN)  | A D) (*FAIL)/x
\= Expect no match
    AbcdCBefgBhiBqz
No match

/(A (.*)   C{0,6} (*THEN)  | A D) z/x
\= Expect no match
    AbcdCBefgBhiBqz
No match

/(A (.*)   (CE){0,6} (*THEN)  | A D) (*FAIL)/x
\= Expect no match
    AbcdCEBefgBhiBqz
No match

/(A (.*)   (CE){0,6} (*THEN)  | A D) z/x
\= Expect no match
    AbcdCEBefgBhiBqz
No match

/(A (.*)   (CE*){0,6} (*THEN)  | A D) (*FAIL)/x
\= Expect no match
    AbcdCBefgBhiBqz
No match

/(A (.*)   (CE*){0,6} (*THEN)  | A D) z/x
\= Expect no match
    AbcdCBefgBhiBqz
No match

/(?=a(*COMMIT)b|ac)ac|ac/
\= Expect no match
    ac
No match

/(?=a(*COMMIT)b|(ac)) ac | (a)c/x
\= Expect no match
    ac
No match

# ----

/(?(?!b(*THEN)a)bn|bnn)/
    bnn 
 0: bn

/(?!b(*SKIP)a)bn|bnn/
    bnn
 0: bn
    
/(?(?!b(*SKIP)a)bn|bnn)/
    bnn 
 0: bn

/(?!b(*PRUNE)a)bn|bnn/
    bnn
 0: bn
    
/(?(?!b(*PRUNE)a)bn|bnn)/
    bnn 
 0: bn
   
/(?!b(*COMMIT)a)bn|bnn/
    bnn
 0: bn
    
/(?(?!b(*COMMIT)a)bn|bnn)/
   bnn 
 0: bn

/(?=b(*SKIP)a)bn|bnn/
\= Expect no match
    bnn
No match

/(?=b(*THEN)a)bn|bnn/
    bnn
 0: bnn
    
/^(?!a(*SKIP)b)/
    ac
 0: 

/^(?!a(*SKIP)b)../
    acd
 0: ac

/(?!a(*SKIP)b)../
    acd
 0: ac

/^(?(?!a(*SKIP)b))/
    ac
 0: 

/^(?!a(*PRUNE)b)../
    acd
 0: ac

/(?!a(*PRUNE)b)../
    acd
 0: ac

/(?!a(*COMMIT)b)ac|cd/
    ac
 0: ac

/\A.*?(?:a|bc)/
    ba
 0: ba

/^(A(*THEN)B|C(*THEN)D)/
    CD           
 0: CD
 1: CD

/(*:m(m)(?&y)(?(DEFINE)(?<y>b))/mark
    abc
 0: b
MK: m(m

/(*PRUNE:m(m)(?&y)(?(DEFINE)(?<y>b))/mark
    abc
 0: b
MK: m(m

/(*SKIP:m(m)(?&y)(?(DEFINE)(?<y>b))/mark
    abc
 0: b

/(*THEN:m(m)(?&y)(?(DEFINE)(?<y>b))/mark
    abc
 0: b
MK: m(m

/^\d*\w{4}/
    1234
 0: 1234
\= Expect no match
    123 
No match

/^[^b]*\w{4}/
    aaaa
 0: aaaa
\= Expect no match
    aaa     
No match

/^[^b]*\w{4}/i
    aaaa
 0: aaaa
\= Expect no match
    aaa     
No match

/^a*\w{4}/
    aaaa
 0: aaaa
\= Expect no match
    aaa     
No match

/^a*\w{4}/i
    aaaa
 0: aaaa
\= Expect no match
    aaa     
No match

/(?:(?<n>foo)|(?<n>bar))\k<n>/dupnames
    foofoo
 0: foofoo
 1: foo
    barbar
 0: barbar
 1: <unset>
 2: bar

/(?<n>A)(?:(?<n>foo)|(?<n>bar))\k<n>/dupnames
    AfooA
 0: AfooA
 1: A
 2: foo
    AbarA  
 0: AbarA
 1: A
 2: <unset>
 3: bar
\= Expect no match 
    Afoofoo
No match
    Abarbar
No match

/^(\d+)\s+IN\s+SOA\s+(\S+)\s+(\S+)\s*\(\s*$/
    1 IN SOA non-sp1 non-sp2(
 0: 1 IN SOA non-sp1 non-sp2(
 1: 1
 2: non-sp1
 3: non-sp2

/^ (?:(?<A>A)|(?'B'B)(?<A>A)) (?('A')x) (?(<B>)y)$/x,dupnames
    Ax
 0: Ax
 1: A
    BAxy 
 0: BAxy
 1: <unset>
 2: B
 3: A
    
/^A\xZ/
    A\0Z 
 0: A\x00Z

/^A\o{123}B/
    A\123B
 0: ASB

/ ^ a + + b $ /x
    aaaab
 0: aaaab
    
/ ^ a + #comment
  + b $ /x
    aaaab
 0: aaaab
    
/ ^ a + #comment
  #comment
  + b $ /x
    aaaab
 0: aaaab
    
/ ^ (?> a + ) b $ /x
    aaaab 
 0: aaaab

/ ^ ( a + ) + + \w $ /x
    aaaab 
 0: aaaab
 1: aaaa

/(?:a\Kb)*+/aftertext
    ababc
 0: b
 0+ c

/(?>a\Kb)*/aftertext
    ababc
 0: b
 0+ c

/(?:a\Kb)*/aftertext
    ababc
 0: b
 0+ c

/(a\Kb)*+/aftertext
    ababc
 0: b
 0+ c
 1: ab

/(a\Kb)*/aftertext
    ababc
 0: b
 0+ c
 1: ab

/(?:x|(?:(xx|yy)+|x|x|x|x|x)|a|a|a)bc/
\= Expect no match
    acb
No match

/\A(?:[^\"]++|\"(?:[^\"]*+|\"\")*+\")++/
    NON QUOTED \"QUOT\"\"ED\" AFTER \"NOT MATCHED
 0: NON QUOTED "QUOT""ED" AFTER 

/\A(?:[^\"]++|\"(?:[^\"]++|\"\")*+\")++/
    NON QUOTED \"QUOT\"\"ED\" AFTER \"NOT MATCHED
 0: NON QUOTED "QUOT""ED" AFTER 

/\A(?:[^\"]++|\"(?:[^\"]++|\"\")++\")++/
    NON QUOTED \"QUOT\"\"ED\" AFTER \"NOT MATCHED
 0: NON QUOTED "QUOT""ED" AFTER 

/\A([^\"1]++|[\"2]([^\"3]*+|[\"4][\"5])*+[\"6])++/
    NON QUOTED \"QUOT\"\"ED\" AFTER \"NOT MATCHED
 0: NON QUOTED "QUOT""ED" AFTER 
 1:  AFTER 
 2: 

/^\w+(?>\s*)(?<=\w)/
    test test
 0: tes

/(?P<same>a)(?P<same>b)/g,dupnames
    abbaba
 0: ab
 1: a
 2: b
 0: ab
 1: a
 2: b

/(?P<same>a)(?P<same>b)(?P=same)/g,dupnames
    abbaba
 0: aba
 1: a
 2: b

/(?P=same)?(?P<same>a)(?P<same>b)/g,dupnames
    abbaba
 0: ab
 1: a
 2: b
 0: ab
 1: a
 2: b

/(?:(?P=same)?(?:(?P=same)(?P<same>a)(?P=same)|(?P=same)?(?P<same>b)(?P=same)){2}(?P=same)(?P<same>c)(?P=same)){2}(?P<same>z)?/g,dupnames
\= Expect no match
    bbbaaaccccaaabbbcc
No match

/(?P<Name>a)?(?P<Name2>b)?(?(<Name>)c|d)*l/
    acl
 0: acl
 1: a
    bdl
 0: bdl
 1: <unset>
 2: b
    adl
 0: dl
    bcl    
 0: l

/\sabc/
    \x{0b}abc
 0: \x0babc

/[\Qa]\E]+/
    aa]]
 0: aa]]

/[\Q]a\E]+/
    aa]]
 0: aa]]

/A((((((((a))))))))\8B/ 
    AaaB
 0: AaaB
 1: a
 2: a
 3: a
 4: a
 5: a
 6: a
 7: a
 8: a

/A(((((((((a)))))))))\9B/ 
    AaaB
 0: AaaB
 1: a
 2: a
 3: a
 4: a
 5: a
 6: a
 7: a
 8: a
 9: a
    
/A[\8\9]B/
    A8B
 0: A8B
    A9B  
 0: A9B

/(|ab)*?d/
   abd
 0: abd
 1: ab
   xyd 
 0: d

/(?:((abcd))|(((?:(?:(?:(?:abc|(?:abcdef))))b)abcdefghi)abc)|((*ACCEPT)))/
    1234abcd
 0: 
 1: <unset>
 2: <unset>
 3: <unset>
 4: <unset>
 5: 

/(\2|a)(\1)/
    aaa
 0: aa
 1: a
 2: a

/(\2)(\1)/

/Z*(|d*){216}/

/(?1)(?#?'){8}(a)/
    baaaaaaaaac
 0: aaaaaaaaa
 1: a

/((((((((((((x))))))))))))\12/
    xx
 0: xx
 1: x
 2: x
 3: x
 4: x
 5: x
 6: x
 7: x
 8: x
 9: x
10: x
11: x
12: x

/A[\8]B[\9]C/
    A8B9C
 0: A8B9C

/(?1)()((((((\1++))\x85)+)|))/
    \x85\x85
 0: \x85\x85
 1: 
 2: \x85\x85
 3: \x85\x85
 4: \x85\x85
 5: \x85
 6: 
 7: 

/(?|(\k'Pm')|(?'Pm'))/
    abcd
 0: 
 1: 

/(?|(aaa)|(b))\g{1}/
    aaaaaa
 0: aaaaaa
 1: aaa
    bb 
 0: bb
 1: b

/(?|(aaa)|(b))(?1)/
    aaaaaa
 0: aaaaaa
 1: aaa
    baaa 
 0: baaa
 1: b
\= Expect no match 
    bb 
No match

/(?|(aaa)|(b))/
    xaaa
 0: aaa
 1: aaa
    xbc 
 0: b
 1: b

/(?|(?'a'aaa)|(?'a'b))\k'a'/
    aaaaaa
 0: aaaaaa
 1: aaa
    bb 
 0: bb
 1: b

/(?|(?'a'aaa)|(?'a'b))(?'a'cccc)\k'a'/dupnames
    aaaccccaaa
 0: aaaccccaaa
 1: aaa
 2: cccc
    bccccb 
 0: bccccb
 1: b
 2: cccc

# /x does not apply to MARK labels 

/x (*MARK:ab cd # comment
ef) x/x,mark
    axxz
 0: xx
MK: ab cd # comment\x0aef

/(?<=a(B){0}c)X/
    acX
 0: X

/(?<DEFINE>b)(?(DEFINE)(a+))(?&DEFINE)/          
    bbbb 
 0: bb
 1: b
\= Expect no match     
    baaab
No match

/(?=.*[A-Z])(?=.*[a-z])(?=.*[0-9])(?=.*[,;:])(?=.{8,16})(?!.*[\s])/
    \   Fred:099
 0: 

/(?=.*X)X$/ 
    \  X
 0: X

/(?s)(?=.*?)b/
    aabc
 0: b

/(Z)(a)\2{1,2}?(?-i)\1X/i
    ZaAAZX
 0: ZaAAZX
 1: Z
 2: a

/(?'c')XX(?'YYYYYYYYYYYYYYYYYYYYYYYCl')/

/[s[:digit:]\E-H]+/
    s09-H
 0: s09-H

/[s[:digit:]\Q\E-H]+/
    s09-H
 0: s09-H

/a+(?:|b)a/
    aaaa
 0: aaaa

/X?(R||){3335}/

/(?1)(A(*COMMIT)|B)D/
    ABD
 0: ABD
 1: B
    XABD
 0: ABD
 1: B
    BAD
 0: BAD
 1: A
    ABXABD  
 0: ABD
 1: B
\= Expect no match 
    ABX 
No match

/(?(DEFINE)(?<m> 1? (?=(?<cond>2)?) 1 2 (?('cond')|3)))
    \A
    ()
    (?&m)
    \Z/x
    123
 0: 123
 1: <unset>
 2: <unset>
 3: 

/^(?: 
(?: A| (1? (?=(?<cond>2)?) (1) 2 (?('cond')|3)) )
(Z)
)+$/x
    AZ123Z
 0: AZ123Z
 1: 123
 2: <unset>
 3: 1
 4: Z
\= Expect no match     
    AZ12Z 
No match
    
/^ (?(DEFINE) ( (?!(a)\2b)..) )   ()(?1)  /x
    acb
 0: ac
 1: <unset>
 2: <unset>
 3: 
\= Expect no match     
    aab
No match
    
/(?>ab|abab){1,5}?M/
    abababababababababababM
 0: abababababM

/(?>ab|abab){2}?M/
    abababM
 0: ababM

/((?(?=(a))a)+k)/
    bbak
 0: ak
 1: ak
 2: a

/((?(?=(a))a|)+k)/
    bbak
 0: ak
 1: ak
 2: a

/(?(?!(b))a|b)+k/
    ababbalbbadabak
 0: abak
 1: b

/(?!(b))c|b/
    Ab
 0: b
    Ac 
 0: c

/(?=(b))b|c/
    Ab
 0: b
 1: b
    Ac 
 0: c

/^(.|(.)(?1)\2)$/
    a
 0: a
 1: a
    aba
 0: aba
 1: aba
 2: a
    abcba
 0: abcba
 1: abcba
 2: a
    ababa
 0: ababa
 1: ababa
 2: a
    abcdcba
 0: abcdcba
 1: abcdcba
 2: a

/^((.)(?1)\2|.?)$/
    a
 0: a
 1: a
    aba
 0: aba
 1: aba
 2: a
    abba
 0: abba
 1: abba
 2: a
    abcba
 0: abcba
 1: abcba
 2: a
    ababa
 0: ababa
 1: ababa
 2: a
    abccba
 0: abccba
 1: abccba
 2: a
    abcdcba
 0: abcdcba
 1: abcdcba
 2: a
    abcddcba
 0: abcddcba
 1: abcddcba
 2: a

/^(.)(\1|a(?2))/
    bab
 0: bab
 1: b
 2: ab

/^(.|(.)(?1)?\2)$/
    abcba
 0: abcba
 1: abcba
 2: a
    
/^(?(?=(a))abc|def)/
    abc
 0: abc
 1: a

/^(?(?!(a))def|abc)/
    abc
 0: abc
 1: a

/^(?(?=(a)(*ACCEPT))abc|def)/
    abc
 0: abc
 1: a

/^(?(?!(a)(*ACCEPT))def|abc)/
    abc
 0: abc
 1: a

/^(?1)\d{3}(a)/
    a123a
 0: a123a
 1: a

# This pattern uses a lot of named subpatterns in order to match email
# addresses in various formats. It's a heavy test for named subpatterns. In the
# <atext> group, slash is coded as \x{2f} so that this pattern can also be
# processed by perltest.sh, which does not cater for an escaped delimiter
# within the pattern. $ within the pattern must also be escaped. All $ and @
# characters in subject strings are escaped so that Perl doesn't interpret them
# as variable insertions and " characters must also be escaped for Perl.

# This set of subpatterns is more or less a direct transliteration of the BNF
# definitions in RFC2822, without any of the obsolete features. The addition of
# a possessive + to the definition of <phrase> reduced the match limit in PCRE2
# from over 5 million to just under 400, and eliminated a very noticeable delay
# when this file was passed to perltest.sh.

/(?ix)(?(DEFINE)
(?<addr_spec>       (?&local_part) \@ (?&domain) )
(?<angle_addr>      (?&CFWS)?+ < (?&addr_spec) > (?&CFWS)?+ )
(?<atext>           [a-z\d!#\$%&'*+-\x{2f}=?^_`{|}~] )
(?<atom>            (?&CFWS)?+ (?&atext)+ (?&CFWS)?+ )
(?<ccontent>        (?&ctext) | (?&quoted_pair) | (?&comment) )
(?<ctext>           [^\x{9}\x{10}\x{13}\x{7f}-\x{ff}\ ()\\] )
(?<comment>         \( (?: (?&FWS)?+ (?&ccontent) )*+ (?&FWS)?+ \) )
(?<CFWS>            (?: (?&FWS)?+ (?&comment) )* (?# NOT possessive)
                    (?: (?&FWS)?+ (?&comment) | (?&FWS) ) )
(?<dcontent>        (?&dtext) | (?&quoted_pair) )
(?<display_name>    (?&phrase) )
(?<domain>          (?&dot_atom) | (?&domain_literal) )
(?<domain_literal>  (?&CFWS)?+ \[ (?: (?&FWS)?+ (?&dcontent) )* (?&FWS)?+ \]
                    (?&CFWS)?+ )
(?<dot_atom>        (?&CFWS)?+ (?&dot_atom_text) (?&CFWS)?+ )
(?<dot_atom_text>   (?&atext)++ (?: \. (?&atext)++)*+ )
(?<dtext>           [^\x{9}\x{10}\x{13}\x{7f}-\x{ff}\ \[\]\\] )
(?<FWS>             (?: [\t\ ]*+ \n)?+ [\t\ ]++ )
(?<local_part>      (?&dot_atom) | (?&quoted_string)  )
(?<mailbox>         (?&name_addr) | (?&addr_spec) )
(?<name_addr>       (?&display_name)? (?&angle_addr) )
(?<phrase>          (?&word)++ )
(?<qcontent>        (?&qtext) | (?&quoted_pair) )
(?<quoted_pair>     " (?&text) )
(?<quoted_string>   (?&CFWS)?+ " (?: (?&FWS)?+ (?&qcontent))* (?&FWS)?+ "
                    (?&CFWS)?+ )
(?<qtext>           [^\x{9}\x{10}\x{13}\x{7f}-\x{ff}\ "\\] )
(?<text>            [^\r\n] )
(?<word>            (?&atom) | (?&quoted_string) )
) # End DEFINE
^(?&mailbox)$/
    Alan Other <user\@dom.ain>
 0: Alan Other <user@dom.ain>
    <user\@dom.ain>
 0: <user@dom.ain>
    user\@dom.ain
 0: user@dom.ain
    user\@[] 
 0: user@[]
    user\@[domain literal] 
 0: user@[domain literal]
    user\@[domain literal with \"[square brackets\"] inside] 
 0: user@[domain literal with "[square brackets"] inside]
    \"A. Other\" <user.1234\@dom.ain> (a comment)
 0: "A. Other" <user.1234@dom.ain> (a comment)
    A. Other <user.1234\@dom.ain> (a comment)
 0: A. Other <user.1234@dom.ain> (a comment)
    \"/s=user/ou=host/o=place/prmd=uu.yy/admd= /c=gb/\"\@x400-re.lay
 0: "/s=user/ou=host/o=place/prmd=uu.yy/admd= /c=gb/"@x400-re.lay
\= Expect no match
    A missing angle <user\@some.where
No match
    The quick brown fox
No match
    
# -------------------------------------------------------------------------- 

# This pattern uses named groups to match default PCRE2 patterns. It's another
# heavy test for named subpatterns. Once again, code slash as \x{2f} and escape 
# $ even in classes so that this works with pcre2test.

/(?sx)(?(DEFINE)

(?<assertion>         (?&simple_assertion) | (?&lookaround) )

(?<atomic_group>      \( \? > (?&regex) \) )

(?<back_reference>    \\ \d+ |
                      \\g (?: [+-]?\d+ | \{ (?: [+-]?\d+ | (?&groupname) ) \} ) |
                      \\k <(?&groupname)> |
                      \\k '(?&groupname)' |
                      \\k \{ (?&groupname) \} |
                      \( \? P= (?&groupname) \) )

(?<branch>            (?:(?&assertion) |
                         (?&callout) |
                         (?&comment) |
                         (?&option_setting) |
                         (?&qualified_item) |
                         (?&quoted_string) |
                         (?&quoted_string_empty) | 
                         (?&special_escape) |
                         (?&verb)
                      )* )

(?<callout>           \(\?C (?: \d+ | 
                      (?: (?<D>["'`^%\#\$]) 
                        (?: \k'D'\k'D' | (?!\k'D') . )* \k'D' |
                      \{ (?: \}\} | [^}]*+ )* \} ) 
                      )? \) )

(?<capturing_group>   \( (?: \? P? < (?&groupname) > | \? ' (?&groupname) ' )?
                      (?&regex) \) )

(?<character_class>   \[ \^?+ (?: \] (?&class_item)* | (?&class_item)+ ) \] )

(?<character_type>    (?! \\N\{\w+\} ) \\ [dDsSwWhHvVRN] )

(?<class_item>        (?: \[ : (?:
                      alnum|alpha|ascii|blank|cntrl|digit|graph|lower|print|
                      punct|space|upper|word|xdigit
                      ) : \] |
                      (?&quoted_string) |  
                      (?&quoted_string_empty) | 
                      (?&escaped_character) | 
                      (?&character_type) | 
                      [^]] ) )

(?<comment>           \(\?\# [^)]* \) | (?&quoted_string_empty) | \\E )

(?<condition>         (?: \( [+-]? \d+ \) |
                          \( < (?&groupname) > \) |
                          \( ' (?&groupname) ' \) |
                          \( R \d* \) |
                          \( R & (?&groupname) \) |
                          \( (?&groupname) \) | 
                          \( DEFINE \) |
                          \( VERSION >?=\d+(?:\.\d\d?)? \) |
                          (?&callout)?+ (?&comment)* (?&lookaround) ) )

(?<conditional_group> \(\? (?&condition) (?&branch) (?: \| (?&branch) )? \) )

(?<delimited_regex>   (?<delimiter> [-\x{2f}!"'`=_:;,%&@~]) (?&regex) 
                      \k'delimiter' .* )

(?<escaped_character> \\ (?: 0[0-7]{1,2} | [0-7]{1,3} | o\{ [0-7]+ \} |
                      x \{ (*COMMIT) [[:xdigit:]]* \} | x [[:xdigit:]]{0,2} | 
                      [aefnrt] | c[[:print:]] |
                      [^[:alnum:]] ) )

(?<group>             (?&capturing_group) | (?&non_capturing_group) |
                      (?&resetting_group) | (?&atomic_group) |
                      (?&conditional_group) )

(?<groupname>         [a-zA-Z_]\w* )

(?<literal_character> (?! (?&range_qualifier) ) [^[()|*+?.\$\\] )

(?<lookaround>        \(\? (?: = | ! | <= | <! ) (?&regex) \) )

(?<non_capturing_group> \(\? [iJmnsUx-]* : (?&regex) \) )

(?<option_setting>    \(\? [iJmnsUx-]* \) )

(?<qualified_item>    (?:\. |
                         (?&lookaround) |
                         (?&back_reference) |
                         (?&character_class) |
                         (?&character_type) |
                         (?&escaped_character) |
                         (?&group) |
                         (?&subroutine_call) |
                         (?&literal_character) |
                         (?&quoted_string) 
                      ) (?&comment)? (?&qualifier)? )

(?<qualifier>         (?: [?*+] | (?&range_qualifier) ) [+?]? )

(?<quoted_string>     (?: \\Q (?: (?!\\E | \k'delimiter') . )++ (?: \\E | ) ) ) 
                      
(?<quoted_string_empty>  \\Q\\E ) 

(?<range_qualifier>   \{ (?: \d+ (?: , \d* )? | , \d+ ) \} )

(?<regex>             (?&start_item)* (?&branch) (?: \| (?&branch) )* )

(?<resetting_group>   \( \? \| (?&regex) \) )

(?<simple_assertion>  \^ | \$ | \\A | \\b | \\B | \\G | \\z | \\Z )

(?<special_escape>    \\K )

(?<start_item>        \( \* (?:
                      ANY |
                      ANYCRLF |
                      BSR_ANYCRLF |
                      BSR_UNICODE |
                      CR |
                      CRLF |
                      LF |
                      LIMIT_MATCH=\d+ |
                      LIMIT_DEPTH=\d+ |
                      LIMIT_HEAP=\d+ | 
                      NOTEMPTY |
                      NOTEMPTY_ATSTART |
                      NO_AUTO_POSSESS |
                      NO_DOTSTAR_ANCHOR |
                      NO_JIT |
                      NO_START_OPT |
                      NUL |
                      UTF |
                      UCP ) \) )

(?<subroutine_call>   (?: \(\?R\) | \(\?[+-]?\d+\) |
                      \(\? (?: & | P> ) (?&groupname) \) |
                      \\g < (?&groupname) > |
                      \\g ' (?&groupname) ' |
                      \\g < [+-]? \d+ > |
                      \\g ' [+-]? \d+ ) )

(?<verb>              \(\* (?: ACCEPT | FAIL | F | COMMIT |
                      (?:MARK)?:(?&verbname) |
                      (?:PRUNE|SKIP|THEN) (?: : (?&verbname)? )? ) \) )

(?<verbname>          [^)]+ )

) # End DEFINE
# Kick it all off...
^(?&delimited_regex)$/subject_literal,jitstack=256
    /^(a)(b)(c)(d)(e)(f)(g)(h)(i)(j)(k)\11*(\3\4)\1(?#)2$/
 0: /^(a)(b)(c)(d)(e)(f)(g)(h)(i)(j)(k)\11*(\3\4)\1(?#)2$/
    /(cat(a(ract|tonic)|erpillar)) \1()2(3)/
 0: /(cat(a(ract|tonic)|erpillar)) \1()2(3)/
    /^From +([^ ]+) +[a-zA-Z][a-zA-Z][a-zA-Z] +[a-zA-Z][a-zA-Z][a-zA-Z] +[0-9]?[0-9] +[0-9][0-9]:[0-9][0-9]/
 0: /^From +([^ ]+) +[a-zA-Z][a-zA-Z][a-zA-Z] +[a-zA-Z][a-zA-Z][a-zA-Z] +[0-9]?[0-9] +[0-9][0-9]:[0-9][0-9]/
    /^From\s+\S+\s+([a-zA-Z]{3}\s+){2}\d{1,2}\s+\d\d:\d\d/
 0: /^From\s+\S+\s+([a-zA-Z]{3}\s+){2}\d{1,2}\s+\d\d:\d\d/
    /<tr([\w\W\s\d][^<>]{0,})><TD([\w\W\s\d][^<>]{0,})>([\d]{0,}\.)(.*)((<BR>([\w\W\s\d][^<>]{0,})|[\s]{0,}))<\/a><\/TD><TD([\w\W\s\d][^<>]{0,})>([\w\W\s\d][^<>]{0,})<\/TD><TD([\w\W\s\d][^<>]{0,})>([\w\W\s\d][^<>]{0,})<\/TD><\/TR>/is
 0: /<tr([\w\W\s\d][^<>]{0,})><TD([\w\W\s\d][^<>]{0,})>([\d]{0,}\.)(.*)((<BR>([\w\W\s\d][^<>]{0,})|[\s]{0,}))<\/a><\/TD><TD([\w\W\s\d][^<>]{0,})>([\w\W\s\d][^<>]{0,})<\/TD><TD([\w\W\s\d][^<>]{0,})>([\w\W\s\d][^<>]{0,})<\/TD><\/TR>/is
    /^(?(DEFINE) (?<A> a) (?<B> b) )  (?&A) (?&B) /
 0: /^(?(DEFINE) (?<A> a) (?<B> b) )  (?&A) (?&B) /
    /(?(DEFINE)(?<byte>2[0-4]\d|25[0-5]|1\d\d|[1-9]?\d))\b(?&byte)(\.(?&byte)){3}/
 0: /(?(DEFINE)(?<byte>2[0-4]\d|25[0-5]|1\d\d|[1-9]?\d))\b(?&byte)(\.(?&byte)){3}/
    /\b(?&byte)(\.(?&byte)){3}(?(DEFINE)(?<byte>2[0-4]\d|25[0-5]|1\d\d|[1-9]?\d))/
 0: /\b(?&byte)(\.(?&byte)){3}(?(DEFINE)(?<byte>2[0-4]\d|25[0-5]|1\d\d|[1-9]?\d))/
    /^(\w++|\s++)*$/
 0: /^(\w++|\s++)*$/
    /a+b?(*THEN)c+(*FAIL)/
 0: /a+b?(*THEN)c+(*FAIL)/
    /(A (A|B(*ACCEPT)|C) D)(E)/x
 0: /(A (A|B(*ACCEPT)|C) D)(E)/x
    /^\W*+(?:((.)\W*+(?1)\W*+\2|)|((.)\W*+(?3)\W*+\4|\W*+.\W*+))\W*+$/i
 0: /^\W*+(?:((.)\W*+(?1)\W*+\2|)|((.)\W*+(?3)\W*+\4|\W*+.\W*+))\W*+$/i
    /A(*PRUNE)B(*SKIP)C(*THEN)D(*COMMIT)E(*F)F(*FAIL)G(?!)H(*ACCEPT)I/B
 0: /A(*PRUNE)B(*SKIP)C(*THEN)D(*COMMIT)E(*F)F(*FAIL)G(?!)H(*ACCEPT)I/B
    /(?C`a``b`)(?C'a''b')(?C"a""b")(?C^a^^b^)(?C%a%%b%)(?C#a##b#)(?C$a$$b$)(?C{a}}b})/B,callout_info
 0: /(?C`a``b`)(?C'a''b')(?C"a""b")(?C^a^^b^)(?C%a%%b%)(?C#a##b#)(?C$a$$b$)(?C{a}}b})/B,callout_info
    /(?sx)(?(DEFINE)(?<assertion> (?&simple_assertion) | (?&lookaround) )(?<atomic_group> \( \? > (?&regex) \) )(?<back_reference> \\ \d+ | \\g (?: [+-]?\d+ | \{ (?: [+-]?\d+ | (?&groupname) ) \} ) | \\k <(?&groupname)> | \\k '(?&groupname)' | \\k \{ (?&groupname) \} | \( \? P= (?&groupname) \) )(?<branch> (?:(?&assertion) | (?&callout) | (?&comment) | (?&option_setting) | (?&qualified_item) | (?&quoted_string) | (?&quoted_string_empty) | (?&special_escape) | (?&verb) )* )(?<callout> \(\?C (?: \d+ | (?: (?<D>["'`^%\#\$]) (?: \k'D'\k'D' | (?!\k'D') . )* \k'D' | \{ (?: \}\} | [^}]*+ )* \} ) )? \) )(?<capturing_group> \( (?: \? P? < (?&groupname) > | \? ' (?&groupname) ' )? (?&regex) \) )(?<character_class> \[ \^?+ (?: \] (?&class_item)* | (?&class_item)+ ) \] )(?<character_type> (?! \\N\{\w+\} ) \\ [dDsSwWhHvVRN] )(?<class_item> (?: \[ : (?: alnum|alpha|ascii|blank|cntrl|digit|graph|lower|print| punct|space|upper|word|xdigit ) : \] | (?&quoted_string) | (?&quoted_string_empty) | (?&escaped_character) | (?&character_type) | [^]] ) )(?<comment> \(\?\# [^)]* \) | (?&quoted_string_empty) | \\E )(?<condition> (?: \( [+-]? \d+ \) | \( < (?&groupname) > \) | \( ' (?&groupname) ' \) | \( R \d* \) | \( R & (?&groupname) \) | \( (?&groupname) \) | \( DEFINE \) | \( VERSION >?=\d+(?:\.\d\d?)? \) | (?&callout)?+ (?&comment)* (?&lookaround) ) )(?<conditional_group> \(\? (?&condition) (?&branch) (?: \| (?&branch) )? \) )(?<delimited_regex> (?<delimiter> [-\x{2f}!"'`=_:;,%&@~]) (?&regex) \k'delimiter' .* )(?<escaped_character> \\ (?: 0[0-7]{1,2} | [0-7]{1,3} | o\{ [0-7]+ \} | x \{ (*COMMIT) [[:xdigit:]]* \} | x [[:xdigit:]]{0,2} | [aefnrt] | c[[:print:]] | [^[:alnum:]] ) )(?<group> (?&capturing_group) | (?&non_capturing_group) | (?&resetting_group) | (?&atomic_group) | (?&conditional_group) )(?<groupname> [a-zA-Z_]\w* )(?<literal_character> (?! (?&range_qualifier) ) [^[()|*+?.\$\\] )(?<lookaround> \(\? (?: = | ! | <= | <! ) (?&regex) \) )(?<non_capturing_group> \(\? [iJmnsUx-]* : (?&regex) \) )(?<option_setting> \(\? [iJmnsUx-]* \) )(?<qualified_item> (?:\. | (?&lookaround) | (?&back_reference) | (?&character_class) | (?&character_type) | (?&escaped_character) | (?&group) | (?&subroutine_call) | (?&literal_character) | (?&quoted_string) ) (?&comment)? (?&qualifier)? )(?<qualifier> (?: [?*+] | (?&range_qualifier) ) [+?]? )(?<quoted_string> (?: \\Q (?: (?!\\E | \k'delimiter') . )++ (?: \\E | ) ) ) (?<quoted_string_empty> \\Q\\E ) (?<range_qualifier> \{ (?: \d+ (?: , \d* )? | , \d+ ) \} )(?<regex> (?&start_item)* (?&branch) (?: \| (?&branch) )* )(?<resetting_group> \( \? \| (?&regex) \) )(?<simple_assertion> \^ | \$ | \\A | \\b | \\B | \\G | \\z | \\Z )(?<special_escape> \\K )(?<start_item> \( \* (?: ANY | ANYCRLF | BSR_ANYCRLF | BSR_UNICODE | CR | CRLF | LF | LIMIT_MATCH=\d+ | LIMIT_DEPTH=\d+ | LIMIT_HEAP=\d+ | NOTEMPTY | NOTEMPTY_ATSTART | NO_AUTO_POSSESS | NO_DOTSTAR_ANCHOR | NO_JIT | NO_START_OPT | NUL | UTF | UCP ) \) )(?<subroutine_call> (?: \(\?R\) | \(\?[+-]?\d+\) | \(\? (?: & | P> ) (?&groupname) \) | \\g < (?&groupname) > | \\g ' (?&groupname) ' | \\g < [+-]? \d+ > | \\g ' [+-]? \d+ ) )(?<verb> \(\* (?: ACCEPT | FAIL | F | COMMIT | (?:MARK)?:(?&verbname) | (?:PRUNE|SKIP|THEN) (?: : (?&verbname)? )? ) \) )(?<verbname> [^)]+ ))^(?&delimited_regex)$/
 0: /(?sx)(?(DEFINE)(?<assertion> (?&simple_assertion) | (?&lookaround) )(?<atomic_group> \( \? > (?&regex) \) )(?<back_reference> \\ \d+ | \\g (?: [+-]?\d+ | \{ (?: [+-]?\d+ | (?&groupname) ) \} ) | \\k <(?&groupname)> | \\k '(?&groupname)' | \\k \{ (?&groupname) \} | \( \? P= (?&groupname) \) )(?<branch> (?:(?&assertion) | (?&callout) | (?&comment) | (?&option_setting) | (?&qualified_item) | (?&quoted_string) | (?&quoted_string_empty) | (?&special_escape) | (?&verb) )* )(?<callout> \(\?C (?: \d+ | (?: (?<D>["'`^%\#\$]) (?: \k'D'\k'D' | (?!\k'D') . )* \k'D' | \{ (?: \}\} | [^}]*+ )* \} ) )? \) )(?<capturing_group> \( (?: \? P? < (?&groupname) > | \? ' (?&groupname) ' )? (?&regex) \) )(?<character_class> \[ \^?+ (?: \] (?&class_item)* | (?&class_item)+ ) \] )(?<character_type> (?! \\N\{\w+\} ) \\ [dDsSwWhHvVRN] )(?<class_item> (?: \[ : (?: alnum|alpha|ascii|blank|cntrl|digit|graph|lower|print| punct|space|upper|word|xdigit ) : \] | (?&quoted_string) | (?&quoted_string_empty) | (?&escaped_character) | (?&character_type) | [^]] ) )(?<comment> \(\?\# [^)]* \) | (?&quoted_string_empty) | \\E )(?<condition> (?: \( [+-]? \d+ \) | \( < (?&groupname) > \) | \( ' (?&groupname) ' \) | \( R \d* \) | \( R & (?&groupname) \) | \( (?&groupname) \) | \( DEFINE \) | \( VERSION >?=\d+(?:\.\d\d?)? \) | (?&callout)?+ (?&comment)* (?&lookaround) ) )(?<conditional_group> \(\? (?&condition) (?&branch) (?: \| (?&branch) )? \) )(?<delimited_regex> (?<delimiter> [-\x{2f}!"'`=_:;,%&@~]) (?&regex) \k'delimiter' .* )(?<escaped_character> \\ (?: 0[0-7]{1,2} | [0-7]{1,3} | o\{ [0-7]+ \} | x \{ (*COMMIT) [[:xdigit:]]* \} | x [[:xdigit:]]{0,2} | [aefnrt] | c[[:print:]] | [^[:alnum:]] ) )(?<group> (?&capturing_group) | (?&non_capturing_group) | (?&resetting_group) | (?&atomic_group) | (?&conditional_group) )(?<groupname> [a-zA-Z_]\w* )(?<literal_character> (?! (?&range_qualifier) ) [^[()|*+?.\$\\] )(?<lookaround> \(\? (?: = | ! | <= | <! ) (?&regex) \) )(?<non_capturing_group> \(\? [iJmnsUx-]* : (?&regex) \) )(?<option_setting> \(\? [iJmnsUx-]* \) )(?<qualified_item> (?:\. | (?&lookaround) | (?&back_reference) | (?&character_class) | (?&character_type) | (?&escaped_character) | (?&group) | (?&subroutine_call) | (?&literal_character) | (?&quoted_string) ) (?&comment)? (?&qualifier)? )(?<qualifier> (?: [?*+] | (?&range_qualifier) ) [+?]? )(?<quoted_string> (?: \\Q (?: (?!\\E | \k'delimiter') . )++ (?: \\E | ) ) ) (?<quoted_string_empty> \\Q\\E ) (?<range_qualifier> \{ (?: \d+ (?: , \d* )? | , \d+ ) \} )(?<regex> (?&start_item)* (?&branch) (?: \| (?&branch) )* )(?<resetting_group> \( \? \| (?&regex) \) )(?<simple_assertion> \^ | \$ | \\A | \\b | \\B | \\G | \\z | \\Z )(?<special_escape> \\K )(?<start_item> \( \* (?: ANY | ANYCRLF | BSR_ANYCRLF | BSR_UNICODE | CR | CRLF | LF | LIMIT_MATCH=\d+ | LIMIT_DEPTH=\d+ | LIMIT_HEAP=\d+ | NOTEMPTY | NOTEMPTY_ATSTART | NO_AUTO_POSSESS | NO_DOTSTAR_ANCHOR | NO_JIT | NO_START_OPT | NUL | UTF | UCP ) \) )(?<subroutine_call> (?: \(\?R\) | \(\?[+-]?\d+\) | \(\? (?: & | P> ) (?&groupname) \) | \\g < (?&groupname) > | \\g ' (?&groupname) ' | \\g < [+-]? \d+ > | \\g ' [+-]? \d+ ) )(?<verb> \(\* (?: ACCEPT | FAIL | F | COMMIT | (?:MARK)?:(?&verbname) | (?:PRUNE|SKIP|THEN) (?: : (?&verbname)? )? ) \) )(?<verbname> [^)]+ ))^(?&delimited_regex)$/
\= Expect no match
    /((?(?C'')\QX\E(?!((?(?C'')(?!X=X));=)r*X=X));=)/
No match
    /(?:(?(2y)a|b)(X))+/
No match
    /a(*MARK)b/
No match
    /a(*CR)b/
No match
    /(?P<abn>(?P=abn)(?<badstufxxx)/
No match

# -------------------------------------------------------------------------- 

/<(?x:[a b])>/xx
    < >
 0: < >

/<(?:[a b])>/xx
    < >
No match

/<(?xxx:[a b])>/
    < >
No match
    
/<(?-x:[a b])>/xx
    < >
 0: < >

/[[:digit:]-]+/
    12-24
 0: 12-24

/((?<=((*ACCEPT)) )\1?\b) /
\= Expect no match     
    ((?<=((*ACCEPT)) )\\1?\\b)\x20
No match

/((?<=((*ACCEPT))X)\1?Y)\1/
    XYYZ
 0: YY
 1: Y
 2: 

/((?<=((*ACCEPT))X)\1?Y(*ACCEPT))\1/
    XYYZ
 0: Y
 1: Y
 2: 

/(?(DEFINE)(?<optional_a>a?)X)^(?&optional_a)a$/
    aa
 0: aa
    a
 0: a

/^(a?)b(?1)a/
    abaa
 0: abaa
 1: a
    aba 
 0: aba
 1: a
    baa
 0: baa
 1: 
    ba  
 0: ba
 1: 

/^(a?)+b(?1)a/
    abaa
 0: abaa
 1: 
    aba 
 0: aba
 1: 
    baa
 0: baa
 1: 
    ba  
 0: ba
 1: 

/^(a?)++b(?1)a/
    abaa
 0: abaa
 1: 
    aba 
 0: aba
 1: 
    baa
 0: baa
 1: 
    ba  
 0: ba
 1: 

/^(a?)+b/
    b
 0: b
 1: 
    ab
 0: ab
 1: 
    aaab 
 0: aaab
 1: 

/(?=a+)a(a+)++b/
    aab
 0: aab
 1: a

/(?<=\G.)/g,aftertext
    abc
 0: 
 0+ bc
 0: 
 0+ c
 0: 
 0+ 

/(?<=(?=.)?)/

/(?<=(?=.)?+)/

/(?<=(?=.)*)/

/(?<=(?=.){4,5})/

/(?<=(?=.){4,5}x)/

/a(?=.(*:X))(*SKIP:X)(*F)|(.)/
    abc
 0: a
 1: a

/a(?>(*:X))(*SKIP:X)(*F)|(.)/
    abc
 0: a
 1: a

/a(?:(*:X))(*SKIP:X)(*F)|(.)/
    abc
 0: b
 1: b

#pattern no_start_optimize

/(?>a(*:1))(?>b(*:1))(*SKIP:1)x|.*/
    abc
 0: abc

/(?>a(*:1))(?>b)(*SKIP:1)x|.*/
    abc
 0: abc

#subject mark

/a(*ACCEPT:X)b/
    abc
 0: a
MK: X
    
/(?=a(*ACCEPT:QQ)bc)axyz/
    axyz
 0: axyz
MK: QQ

/(?(DEFINE)(a(*ACCEPT:X)))(?1)b/
    abc
 0: ab
MK: X
    
/a(*F:X)b/
    abc
No match, mark = X
    
/(?(DEFINE)(a(*F:X)))(?1)b/
    abc
No match, mark = X

/a(*COMMIT:X)b/
    abc
 0: ab
MK: X
    
/(?(DEFINE)(a(*COMMIT:X)))(?1)b/
    abc
 0: ab
MK: X
    
/a+(*:Z)b(*COMMIT:X)(*SKIP:Z)c|.*/
    aaaabd
 0: bd

/a+(*:Z)b(*COMMIT:X)(*SKIP:X)c|.*/
    aaaabd
No match, mark = X

/a(*COMMIT:X)b/
    axabc
No match, mark = X

#pattern -no_start_optimize
#subject -mark 

/(.COMMIT)(*COMMIT::::::::::interal error:::)/

/(*COMMIT:��)/

/(*COMMIT:]w)/

/(?i)A(?^)B(?^x:C D)(?^i)e f/
    aBCDE F
 0: aBCDE F
\= Expect no match
    aBCDEF
No match
    AbCDe f
No match

/(*pla:foo).{6}/
    abcfoobarxyz
 0: foobar
\= Expect no match
    abcfooba
No match

/(*positive_lookahead:foo).{6}/
    abcfoobarxyz
 0: foobar
    
/(?(*pla:foo).{6}|a..)/
    foobarbaz
 0: foobar
    abcfoobar       
 0: abc

/(?(*positive_lookahead:foo).{6}|a..)/
    foobarbaz
 0: foobar
    abcfoobar       
 0: abc
    
/(*plb:foo)bar/
    abcfoobar
 0: bar
\= Expect no match
    abcbarfoo     
No match

/(*positive_lookbehind:foo)bar/
    abcfoobar
 0: bar
\= Expect no match
    abcbarfoo
No match
    
/(?(*plb:foo)bar|baz)/
    abcfoobar
 0: bar
    bazfoobar
 0: baz
    abcbazfoobar
 0: baz
    foobazfoobar    
 0: bar
 
/(?(*positive_lookbehind:foo)bar|baz)/
    abcfoobar
 0: bar
    bazfoobar
 0: baz
    abcbazfoobar
 0: baz
    foobazfoobar    
 0: bar
 
/(*nlb:foo)bar/
    abcbarfoo     
 0: bar
\= Expect no match
    abcfoobar
No match

/(*negative_lookbehind:foo)bar/
    abcbarfoo     
 0: bar
\= Expect no match
    abcfoobar
No match
    
/(?(*nlb:foo)bar|baz)/
    abcfoobaz 
 0: baz
    abcbarbaz 
 0: bar
\= Expect no match
    abcfoobar
No match
 
/(?(*negative_lookbehind:foo)bar|baz)/
    abcfoobaz 
 0: baz
    abcbarbaz 
 0: bar
\= Expect no match
    abcfoobar
No match
 
/(*atomic:a+)\w/
    aaab
 0: aaab
\= Expect no match
    aaaa      
No match

/   (?<word> \w+ )*    \.   /xi
    pokus.
 0: pokus.
 1: pokus
    
/(?(DEFINE) (?<word> \w+ ) ) (?&word)*   \./xi
    pokus.
 0: pokus.

/(?(DEFINE) (?<word> \w+ ) ) ( (?&word)* )   \./xi 
    pokus.
 0: pokus.
 1: <unset>
 2: pokus

/(?&word)*  (?(DEFINE) (?<word> \w+ ) )  \./xi
    pokus.
 0: pokus.

/(?&word)*  \. (?<word> \w+ )/xi
    pokus.hokus
 0: pokus.hokus
 1: hokus

/a(?(?=(*:2)b).)/mark
    abc
 0: ab
MK: 2
    acb     
 0: a

/a(?(?!(*:2)b).)/mark
    acb
 0: ac
    abc     
 0: a
MK: 2

/(?:a|ab){1}+c/
\= Expect no match
    abc
No match

/(a|ab){1}+c/
    abc
No match
    
/(a+){1}+a/
\= Expect no match
    aaaa
No match

/(?(DEFINE)(a|ab))(?1){1}+c/
    abc    
No match

/(?:a|(?=b)|.)*\z/
    abc
 0: abc
    
/(?:a|(?=b)|.)*/
    abc 
 0: a
    
/(?<=a(*SKIP)x)|c/
    abcd
No match
    
/(?<=a(*SKIP)x)|d/
    abcd
 0: d
 
/(?<=(?=.(?<=x)))/aftertext
    abx
 0: 
 0+ x

/(?<=(?=(?<=a)))b/
    ab
 0: b

/^(?<A>a)(?(<A>)b)((?<=b).*)$/
    abc
 0: abc
 1: a
 2: c

/^(a\1?){4}$/
    aaaa
 0: aaaa
 1: a
    aaaaaa
 0: aaaaaa
 1: aa

/^((\1+)|\d)+133X$/
    111133X
 0: 111133X
 1: 11
 2: 11

/^(?>.*?([A-Z])(?!.*\1)){26}/i
    The quick brown fox jumps over the lazy dog.
 0: The quick brown fox jumps over the lazy dog
 1: g
    Jackdaws love my big sphinx of quartz.
 0: Jackdaws love my big sphinx of quartz
 1: z
    Pack my box with five dozen liquor jugs.
 0: Pack my box with five dozen liquor jugs
 1: s
\= Expect no match
    The quick brown fox jumps over the lazy cat.
No match
    Hackdaws love my big sphinx of quartz.
No match
    Pack my fox with five dozen liquor jugs.
No match

/(?<=X(?(DEFINE)(A)))X(*F)/
\= Expect no match
    AXYZ
No match

/(?<=X(?(DEFINE)(A)))./
    AXYZ
 0: Y

/(?<=X(?(DEFINE)(.*))Y)./
    AXYZ
 0: Z

/(?<=X(?(DEFINE)(Y))(?1))./
    AXYZ
 0: Z

/(?(DEFINE)(?<foo>bar))(?<![-a-z0-9])word/
    word
 0: word

/a{1,2,3}b/
    a{1,2,3}b
 0: a{1,2,3}b

/\214748364/
    >\x{8c}748364<
 0: \x8c748364
    
/a{65536/
    >a{65536<
 0: a{65536

/a\K.(?0)*/
    abac
 0: c

/(a\K.(?1)*)/
    abac
 0: c
 1: abac

# -------------------------------------------------------------------------- 
# Perl-compatible tests of variable-length lookbehinds.

/(?<=ab?c).../g
    abcdefgacxyz
 0: def
 0: xyz

/(?<=PQR|ab?c).../g
    abcdefgacxyzPQR123
 0: def
 0: xyz
 0: 123

/(?<=ab?c|PQR).../g
    abcdefgacxyzPQR123
 0: def
 0: xyz
 0: 123

/(?<=PQ|ab?c).../g
    abcdefgacxyzPQR123
 0: def
 0: xyz
 0: R12

/(?<=ab?c|PQ).../g
    abcdefgacxyzPQR123
 0: def
 0: xyz
 0: R12

/(?<=a(b?c|d?e?e)f)X./g
     acfX1zzzaefX2zzzadeefX3zzzX4zzz
 0: X1
 1: c
 0: X2
 1: e
 0: X3
 1: dee

/(?<!a(b?c|d?e?e)f)X./g
     acfX1zzzaefX2zzzadeefX3zzzX4zzz
 0: X4
     
/(?(?<=ab?c)d|e)/
    abcdefg
 0: d
    acdefg
 0: d
    axdefg
 0: e
    
/(?<=\d{2,3}|ABC)./
    ABCD   
 0: D

/(?<=(\d{1,255}))X/
    1234X
 0: X
 1: 1234

/(?<=a(b?c){3}d)X/
   ZXacbccdXYZ
 0: X
 1: c
   
/(?<=a(b?c){0}d)X/
   ZXadXYZ
 0: X
 
/(?<=a?(b?c){0}d)X./
   ZXadXYZ
 0: XY
 
/(?<=\R)X/
    \x{0a}X
 0: X
    a\x{0a}X
 0: X
    a\x{0d}\x{0a}X
 0: X

# -------------------------------------------------------------------------- 

# Altered interpretation of {,n}

/a{,3}B/
    XBBB
 0: B
    XaBBB
 0: aB
    XaaBBB
 0: aaB
    XaaaBBB
 0: aaaB
    XaaaaBBB
 0: aaaB

# But {,} remains not a qualifier

/a{,}B/
    Xa{,}BBB
 0: a{,}B
\= Expect no match     
    XBBB
No match
    XaBBB
No match
    
# Checks for non-quantifiers after refactored code

/X{/
    ZZX{}YY
 0: X{

/X{A/
    ZZX{ABC}
 0: X{A

/X{}/
    ZZX{}YZ
 0: X{}
    
/X{1234/
    ZZX{123456
 0: X{1234
    
/X{12ABC}/ 
    ZZX{12ABC}Y
 0: X{12ABC}
    
/X{1,/
    ZZX{1,...
 0: X{1,
    
/X{,9/
    ZZX{,9}abc
 0: X{,9
    
/X{,9]/
    ZZX{,9]..   
 0: X{,9]
    
# -------------------------------------------------------------------------- 

/(A)(?-1)(?+1)(B)/
    xxAABBzz
 0: AABB
 1: A
 2: B
   
/(A)(\g{ -2 }B)/
    XAABX
 0: AAB
 1: A
 2: AB

/(A)((?-2)B)/
    XAABX
 0: AAB
 1: A
 2: AB

/a\c\X/
    --a\x1cX--
 0: a\x1cX
    
/(a)\g{ 1 }/
    baab
 0: aa
 1: a

/a{ 1,2 }/
    Xaaaaa
 0: aa

/a{ 1 , 2 }/
    Xaaaaa
 0: aa

/(?'name'ab)\k{ name }(?P=name)/
    XabababX 
 0: ababab
 1: ab

/A{,}B/
    A{,}B
 0: A{,}B

/A{ , }B/
    A{ , }B
 0: A{ , }B
    
/A{ ,3}/
    AAAAAACC 
 0: AAA

/A{ 3, }/
    BBAAAAAACC 
 0: AAAAAA

# This pattern validates regular expression patterns. The original that I was
# sent was this:
# /^((?:(?:[^?+*{}()[\]\\|]+|\\.|\[(?:\^?\\.|\^[^\\]|[^\\^])(?:[^\]\\]+|\\.)*\]|\((?:\?[:=!]|\?<[=!]|\?>)?(?1)??\)|\(\?(?:R|[+-]?\d+)\))(?:(?:[?+*]|\{\d+(?:,\d*)?\})[?+]?)?|\|)*)$/
# This is not very readable, and also does not handle all features. I have done
# some work on it.

/^
(?<re>
# A regular expression is zero or more of these items.
  (?:
  # An item is one of these:
    (?:
      [^?+*{}()\[\]\\|]++|  # Non-meta characters or unquoted .
      \\.|                  # Quoted .

      \[                    # Class, which is [
      (?:                   # Followed by
        \^?\\.|             # Optional ^ and any escaped character
        \^[^\\]|            # OR ^ and not escaped character
        [^\\^]              # OR neither ^ nor \
      )                     # Followed by
      (?:[^\]\\]+|\\.)*+    # Zero or more (not ] or \) OR escaped dot
      \]|                   # Class ends with ]

      \(                    # Parenthesized group
        (?:                 # Start with optional
          \?[:=!]|          # ? followed by : = !
          \?<[=!]|          # OR ?< followed by = or !
          \?>               # OR ?>
        )?
        (?&re)??            # Then a nested <re>
      \)|                   # End parenthesized group

      \(\?                  # Other parenthesized items
        (?:                 # (? followed by
          R|                # R
          [+-]?\d++         # Or optional +- and digits
        )
      \)|                   # End parens

      \(\*                  # Verbs
        (?:
          COMMIT|
          FAIL|
          MARK:[^)]*|
          (?:PRUNE|SKIP|THEN)(?::[^\)]*+)?
        )
      \)
    )                       # End list of items

    # Followed by an optional quantifier

    (?:
      (?:
        [?+*]     # ?+*
        |         # OR
        \{\d+     # { digits
        (?:,\d*)? # optionally followed by ,digits
        \}        # then closing }
        |         # OR
        \{,\d+}   # {,digits}
      )
      [?+]?       # optional ungreedy or possessive
    )?

    | # OR an "item" is a branch ending

    \|

  )*  # Zero or more top-level items.
)     # End regex group.
$/x
    [abcdef]
 0: [abcdef]
 1: [abcdef]
    [abc\\]def]
 0: [abc\]def]
 1: [abc\]def]
    a.b|abcd
 0: a.b|abcd
 1: a.b|abcd
    ab()d
 0: ab()d
 1: ab()d
    ab{1,3}d
 0: ab{1,3}d
 1: ab{1,3}d
    ab{,3}d
 0: ab{,3}d
 1: ab{,3}d
    ab(*FAIL)d(*COMMIT)(*SKIP)(*THEN:abc)
 0: ab(*FAIL)d(*COMMIT)(*SKIP)(*THEN:abc)
 1: ab(*FAIL)d(*COMMIT)(*SKIP)(*THEN:abc)
    ab(*MARK:xyz)
 0: ab(*MARK:xyz)
 1: ab(*MARK:xyz)
    (?=.*[A-Z])(?=.*[a-z])(?=.*[0-9])(?=.*[,;:])(?=.{8,16})(?!.*[\\s])
 0: (?=.*[A-Z])(?=.*[a-z])(?=.*[0-9])(?=.*[,;:])(?=.{8,16})(?!.*[\s])
 1: (?=.*[A-Z])(?=.*[a-z])(?=.*[0-9])(?=.*[,;:])(?=.{8,16})(?!.*[\s])
    abcd\\t\\n\\r\\f\\a\\e\\071\\x3b\\^\\\\\\?caxyz
 0: abcd\t\n\r\f\a\e\071\x3b\^\\\?caxyz
 1: abcd\t\n\r\f\a\e\071\x3b\^\\\?caxyz
    a*abc?xyz+pqr{3}ab{2,}xy{4,5}pq{0,6}AB{0,}zz
 0: a*abc?xyz+pqr{3}ab{2,}xy{4,5}pq{0,6}AB{0,}zz
 1: a*abc?xyz+pqr{3}ab{2,}xy{4,5}pq{0,6}AB{0,}zz
    \\G(?:(?=(\\1.|)(.))){1,13}?(?!.*\\2.*\\2)\\1\\K\\2
 0: \G(?:(?=(\1.|)(.))){1,13}?(?!.*\2.*\2)\1\K\2
 1: \G(?:(?=(\1.|)(.))){1,13}?(?!.*\2.*\2)\1\K\2
\= Expect no match
    ab)d
No match
    ab(d
No match
    {4,5}
No match
    a[]b
No match
    (a)(?(1)a|b|c)
No match

/^..A(*SKIP)B|C/
    12ADC
 0: C

/(?<!a?)/
    a
No match

# End of testinput1