CodeMirror PCRE mode

This is a CodeMirror mode that brings syntax highlighting for Perl Compatible Regular Expressions (PCRE).

MIME types defined:

text/x-regex
text/x-pcre-regex

Options:

extended: boolean: initial state of the 'x' flag; default: true.

Table of contents:

Use as nested mode
man pcresyntax
Examples from man pcrepattern
Other details

Use as nested mode

Below are demonstrations of how the PCRE mode can be used to highlight regular expressions within other languages. This first example is an nginx configuration snippet:

This second example is a simple list of one-line regexes with comments:

man pcresyntax

This is a slightly adjusted copy of `man pcresyntax`. This man page reflects most PCRE syntactic structures in a colourful way thanks to CodeMirror and the PCRE mode.

# PCRESYNTAX(3)                                  Library Functions Manual                                 PCRESYNTAX(3)
#
# NAME
#        PCRE - Perl-compatible regular expressions
#
# PCRE REGULAR EXPRESSION SYNTAX SUMMARY
#
#        The  full  syntax  and  semantics  of  the regular expressions that are supported by PCRE are described in the
#        pcrepattern documentation. This document contains a quick-reference summary of the syntax.
#
# QUOTING

\x         where x is non-alphanumeric is a literal x
          \Q...\E    treat enclosed characters as literal

# CHARACTERS

\a       # alarm, that is, the BEL character (hex 07)
          \cx      # "control-x", where x is any ASCII character
          \e       # escape (hex 1B)
          \f       # form feed (hex 0C)
          \n       # newline (hex 0A)
          \r       # carriage return (hex 0D)
          \t       # tab (hex 09)
          \077     # character with octal code 0dd
          \777     # character with octal code ddd, or backreference
          \o{777}  # character with octal code ddd..
          \xff     # character with hex code hh
          \x{fffe} # character with hex code hhh..

#        Note that \0dd is always an octal code, and that \8 and \9 are the literal characters "8" and "9".
#
# CHARACTER TYPES

.        # any character except newline;
                   #   in dotall mode, any character whatsoever
          \C       # one data unit, even in UTF mode (best avoided)
          \d       # a decimal digit
          \D       # a character that is not a decimal digit
          \h       # a horizontal white space character
          \H       # a character that is not a horizontal white space character
          \N       # a character that is not a newline
          \p{Pi}   # a character with the xx property
          \P{Pi}   # a character without the xx property
          \R       # a newline sequence
          \s       # a white space character
          \S       # a character that is not a white space character
          \v       # a vertical white space character
          \V       # a character that is not a vertical white space character
          \w       # a "word" character
          \W       # a "non-word" character
          \X       # a Unicode extended grapheme cluster

#        By default, \d, \s, and \w match only ASCII characters, even in UTF-8 mode or in the 16- bit  and  32-bit  li‐
#        braries.  However,  if  locale-specific  matching  is happening, \s and \w may also match characters with code
#        points in the range 128-255. If the PCRE_UCP option is set, the behaviour of these escape sequences is changed
#        to use Unicode properties and they match many more characters.

# GENERAL CATEGORY PROPERTIES FOR \p and \P

\p{C}       # Other
       \p{Cc}      # Control
       \p{Cf}      # Format
       \p{Cn}      # Unassigned
       \p{Co}      # Private use
       \p{Cs}      # Surrogate

\p{L}       # Letter
       \p{Ll}      # Lower case letter
       \p{Lm}      # Modifier letter
       \p{Lo}      # Other letter
       \p{Lt}      # Title case letter
       \p{Lu}      # Upper case letter
       \p{L&}      # Ll, Lu, or Lt

\p{M}       # Mark
       \p{Mc}      # Spacing mark
       \p{Me}      # Enclosing mark
       \p{Mn}      # Non-spacing mark

\p{N}       # Number
       \p{Nd}      # Decimal number
       \p{Nl}      # Letter number
       \p{No}      # Other number

\p{P}       # Punctuation
       \p{Pc}      # Connector punctuation
       \p{Pd}      # Dash punctuation
       \p{Pe}      # Close punctuation
       \p{Pf}      # Final punctuation
       \p{Pi}      # Initial punctuation
       \p{Po}      # Other punctuation
       \p{Ps}      # Open punctuation

\p{S}       # Symbol
       \p{Sc}      # Currency symbol
       \p{Sk}      # Modifier symbol
       \p{Sm}      # Mathematical symbol
       \p{So}      # Other symbol

\p{Z}       # Separator
       \p{Zl}      # Line separator
       \p{Zp}      # Paragraph separator
       \p{Zs}      # Space separator

# PCRE SPECIAL CATEGORY PROPERTIES FOR \p and \P

\p{Xan}     # Alphanumeric: union of properties L and N
       \p{Xps}     # POSIX space: property Z or tab, NL, VT, FF, CR
       \p{Xsp}     # Perl space: property Z or tab, NL, VT, FF, CR
       \p{Xuc}     # Univerally-named character: one that can be
                   #   represented by a Universal Character Name
       \p{Xwd}     # Perl word: property Xan or underscore

#        Perl  and  POSIX  space  are  now  the same. Perl added VT to its space character set at release 5.18 and PCRE
#        changed at release 8.34.

# SCRIPT NAMES FOR \p AND \P

\p{Arabic}, \p{Armenian}, \p{Avestan}, \p{Balinese}, \p{Bamum}, \p{Bassa_Vah}, \p{Batak}, \p{Bengali},
       \p{Bopomofo}, \p{Brahmi}, \p{Braille}, \p{Buginese}, \p{Buhid}, \p{Canadian_Aboriginal}, \p{Carian},
       \p{Caucasian_Albanian}, \p{Chakma}, \p{Cham}, \p{Cherokee}, \p{Common}, \p{Coptic}, \p{Cuneiform},
       \p{Cypriot}, \p{Cyrillic}, \p{Deseret}, \p{Devanagari}, \p{Duployan}, \p{Egyptian_Hieroglyphs}, \p{Elbasan},
       \p{Ethiopic}, \p{Georgian}, \p{Glagolitic}, \p{Gothic}, \p{Grantha}, \p{Greek}, \p{Gujarati}, \p{Gurmukhi},
       \p{Han}, \p{Hangul}, \p{Hanunoo}, \p{Hebrew}, \p{Hiragana}, \p{Imperial_Aramaic}, \p{Inherited},
       \p{Inscriptional_Pahlavi}, \p{Inscriptional_Parthian}, \p{Javanese}, \p{Kaithi}, \p{Kannada}, \p{Katakana},
       \p{Kayah_Li}, \p{Kharoshthi}, \p{Khmer}, \p{Khojki}, \p{Khudawadi}, \p{Lao}, \p{Latin}, \p{Lepcha}, \p{Limbu},
       \p{Linear_A}, \p{Linear_B}, \p{Lisu}, \p{Lycian}, \p{Lydian}, \p{Mahajani}, \p{Malayalam}, \p{Mandaic},
       \p{Manichaean}, \p{Meetei_Mayek}, \p{Mende_Kikakui}, \p{Meroitic_Cursive}, \p{Meroitic_Hieroglyphs}, \p{Miao},
       \p{Modi}, \p{Mongolian}, \p{Mro}, \p{Myanmar}, \p{Nabataean}, \p{New_Tai_Lue}, \p{Nko}, \p{Ogham},
       \p{Ol_Chiki}, \p{Old_Italic}, \p{Old_North_Arabian}, \p{Old_Permic}, \p{Old_Persian}, \p{Old_South_Arabian},
       \p{Old_Turkic}, \p{Oriya}, \p{Osmanya}, \p{Pahawh_Hmong}, \p{Palmyrene}, \p{Pau_Cin_Hau}, \p{Phags_Pa},
       \p{Phoenician}, \p{Psalter_Pahlavi}, \p{Rejang}, \p{Runic}, \p{Samaritan}, \p{Saurashtra}, \p{Sharada},
       \p{Shavian}, \p{Siddham}, \p{Sinhala}, \p{Sora_Sompeng}, \p{Sundanese}, \p{Syloti_Nagri}, \p{Syriac},
       \p{Tagalog}, \p{Tagbanwa}, \p{Tai_Le}, \p{Tai_Tham}, \p{Tai_Viet}, \p{Takri}, \p{Tamil}, \p{Telugu},
       \p{Thaana}, \p{Thai}, \p{Tibetan}, \p{Tifinagh}, \p{Tirhuta}, \p{Ugaritic}, \p{Vai}, \p{Warang_Citi}, \p{Yi}.

# CHARACTER CLASSES

[...]        # positive character class
       [^...]       # negative character class
       [x-y]        # range (can be used for hex characters)
       [[:word:]]   # positive POSIX named set
       [[:^word:]]  # negative POSIX named set

[[:alnum:]]  # alphanumeric
       [[:alpha:]]  # alphabetic
       [[:ascii:]]  # 0-127
       [[:blank:]]  # space or tab
       [[:cntrl:]]  # control character
       [[:digit:]]  # decimal digit
       [[:graph:]]  # printing, excluding space
       [[:lower:]]  # lower case letter
       [[:print:]]  # printing, including space
       [[:punct:]]  # printing, excluding alphanumeric
       [[:space:]]  # white space
       [[:upper:]]  # upper case letter
       [[:word:]]   # same as \w
       [[:xdigit:]] # hexadecimal digit

#        In  PCRE,  POSIX  character set names recognize only ASCII characters by default, but some of them use Unicode
#        properties if PCRE_UCP is set. You can use \Q...\E inside a character class.

# QUANTIFIERS

?         # 0 or 1, greedy
          ?+        # 0 or 1, possessive
          ??        # 0 or 1, lazy
          *         # 0 or more, greedy
          *+        # 0 or more, possessive
          *?        # 0 or more, lazy
          +         # 1 or more, greedy
          ++        # 1 or more, possessive
          +?        # 1 or more, lazy
          {1}       # exactly n
          {1,6}     # at least n, no more than m, greedy
          {1,6}+    # at least n, no more than m, possessive
          {1,6}?    # at least n, no more than m, lazy
          {1,}      # n or more, greedy
          {1,}+     # n or more, possessive
          {1,}?     # n or more, lazy

# ANCHORS AND SIMPLE ASSERTIONS

\b        # word boundary
          \B        # not a word boundary
          ^         # start of subject
                    #  also after internal newline in multiline mode
          \A        # start of subject
          $         # end of subject
                    #  also before newline at end of subject
                    #  also before internal newline in multiline mode
          \Z        # end of subject
                    #  also before newline at end of subject
          \z        # end of subject
          \G        # first matching position in subject

# MATCH POINT RESET

\K        # reset start of match

#        \K is honoured in positive assertions, but ignored in negative ones.

# ALTERNATION

expr|expr|expr...

# CAPTURING

(...)         # capturing group
          (?<name>...)  # named capturing group (Perl)
          (?'name'...)  # named capturing group (Perl)
          (?P<name>...) # named capturing group (Python)
          (?:...)       # non-capturing group
          (?|...)       # non-capturing group; reset group numbers for
                        #  capturing groups in each alternative

# ATOMIC GROUPS

(?>...)       # atomic, non-capturing group

# COMMENT

(?#....)      # comment (not nestable)

# OPTION SETTING

(?i)          # caseless
          (?J)          # allow duplicate names
          (?m)          # multiline
          (?s)          # single line (dotall)
          (?U)          # default ungreedy (lazy)
          (?x)          # extended (ignore white space)
          (?-iUs)       # unset option(s)

#        The following are recognized only at the very start of a pattern or after one of the  newline  or  \R  options
#        with similar syntax. More than one of them may appear.

(*LIMIT_MATCH=4)     # set the match limit to d (decimal number)
          (*LIMIT_RECURSION=3) # set the recursion limit to d (decimal number)
          (*NO_AUTO_POSSESS)   # no auto-possessification (PCRE_NO_AUTO_POSSESS)
          (*NO_START_OPT)      # no start-match optimization (PCRE_NO_START_OPTIMIZE)
          (*UTF8)              # set UTF-8 mode: 8-bit library (PCRE_UTF8)
          (*UTF16)             # set UTF-16 mode: 16-bit library (PCRE_UTF16)
          (*UTF32)             # set UTF-32 mode: 32-bit library (PCRE_UTF32)
          (*UTF)               # set appropriate UTF mode for the library in use
          (*UCP)               # set PCRE_UCP (use Unicode properties for \d etc)

#        Note  that  LIMIT_MATCH  and  LIMIT_RECURSION  can  only  reduce  the value of the limits set by the caller of
#        pcre_exec(), not increase them.

# NEWLINE CONVENTION

#        These are recognized only at the very start of the pattern or after option settings with a similar syntax.

(*CR)         # carriage return only
          (*LF)         # linefeed only
          (*CRLF)       # carriage return followed by linefeed
          (*ANYCRLF)    # all three of the above
          (*ANY)        # any Unicode newline sequence

# WHAT \R MATCHES

#        These are recognized only at the very start of the pattern or after option setting with a similar syntax.

(*BSR_ANYCRLF) # CR, LF, or CRLF
          (*BSR_UNICODE) # any Unicode newline sequence

# LOOKAHEAD AND LOOKBEHIND ASSERTIONS

(?=...)       # positive look ahead
          (?!...)       # negative look ahead
          (?<=...)      # positive look behind
          (?<!...)      # negative look behind

#        Each top-level branch of a look behind must be of a fixed length.

# BACKREFERENCES

\1            # reference by number (can be ambiguous)
          \g2           # reference by number
          \g{3}         # reference by number
          \g{-4}        # relative reference by number
          \k<name>      # reference by name (Perl)
          \k'name'      # reference by name (Perl)
          \g{name}      # reference by name (Perl)
          \k{name}      # reference by name (.NET)
          (?P=name)     # reference by name (Python)

# SUBROUTINE REFERENCES (POSSIBLY RECURSIVE)

(?R)          # recurse whole pattern
          (?1)          # call subpattern by absolute number
          (?+2)         # call subpattern by relative number
          (?-3)         # call subpattern by relative number
          (?&name)      # call subpattern by name (Perl)
          (?P>name)     # call subpattern by name (Python)
          \g<name>      # call subpattern by name (Oniguruma)
          \g'name'      # call subpattern by name (Oniguruma)
          \g<4>         # call subpattern by absolute number (Oniguruma)
          \g'5'         # call subpattern by absolute number (Oniguruma)
          \g<+6>        # call subpattern by relative number (PCRE extension)
          \g'+7'        # call subpattern by relative number (PCRE extension)
          \g<-8>        # call subpattern by relative number (PCRE extension)
          \g'-9'        # call subpattern by relative number (PCRE extension)

# CONDITIONAL PATTERNS

(?(condition)yes-pattern)
          (?(condition)yes-pattern|no-pattern)

(?(1)...)      # absolute reference condition
          (?(+2)...)     # relative reference condition
          (?(-3)...)     # relative reference condition
          (?(<name>)...) # named reference condition (Perl)
          (?('name')...) # named reference condition (Perl)
          (?(name)...)   # named reference condition (PCRE)
          (?(R)...)      # overall recursion condition
          (?(R4)...)     # specific group recursion condition
          (?(R&name)...) # specific recursion condition
          (?(DEFINE)...) # define subpattern for reference
          (?(?=assert).) # assertion condition

# BACKTRACKING CONTROL

#        The following act immediately they are reached:

(*ACCEPT)     # force successful match
          (*FAIL)       (?# force backtrack; synonym) (*F)
          (*MARK:NAME)  (?# set name to be passed back; synonym) (*:NAME)

#        The following act only when a subsequent match failure causes a backtrack to reach  them.  They  all  force  a
#        match  failure,  but they differ in what happens afterwards. Those that advance the start-of-match point do so
#        only if the pattern is not anchored.

(*COMMIT)     # overall failure, no advance of starting point
          (*PRUNE)      # advance to next starting character
          (*PRUNE:NAME) # equivalent to (*MARK:NAME)(*PRUNE)
          (*SKIP)       # advance to current matching position
          (*SKIP:NAME)  # advance to position corresponding to an earlier
                        # (*MARK:NAME); if not found, the (*SKIP) is ignored
          (*THEN)       # local failure, backtrack to next alternation
          (*THEN:NAME)  # equivalent to (*MARK:NAME)(*THEN)

# CALLOUTS

(?C)    # callout
          (?C255) # callout with data n

# SEE ALSO
#
#        pcrepattern(3), pcreapi(3), pcrecallout(3), pcrematching(3), pcre(3).
#
# AUTHOR
#
#        Philip Hazel
#        University Computing Service
#        Cambridge CB2 3QH, England.
#
# REVISION
#
#        Last updated: 08 January 2014
#        Copyright (c) 1997-2014 University of Cambridge.
#
# PCRE 8.35                                          08 January 2014                                      PCRESYNTAX(3)

Examples from man pcrepattern

`man pcrepattern` is much longer than `man pcresyntax`, which is why only its examples were reproduced below.

(*CR)a.b

\Qabc$xyz\E \Qabc\$xyz\E \Qabc\E\$\Qxyz\E

\040  # is another way of writing an ASCII space
\40   # is the same, provided there are fewer than 40 previous capturing subpatterns
\7    # is always a back reference
\11   # might be a back reference, or another way of writing a tab
\011  # is always a tab
\0113 # is a tab followed by the character "3"
\113  # might be a back reference, otherwise the character with octal code 113
\377  # might be a back reference, otherwise the value 255 (decimal)
\81   # is either a back reference, or the two characters "8" and "1"

\xdc is exactly the same as \x{dc}, or \u00dc in JavaScript mode.

[In addition, inside a character class, \b is interpreted as the backspace character (hex 08).]

[\N is not allowed in a character class.]
[\B, \R, and \X are not special inside a character class.]

# In 8-bit non-UTF-8 mode \R is equivalent to the following:
(?>\r\n|\n|\x0b|\f|\r|\x85)

foo\Kbar
(foo)\Kbar
^abc$

(?|	(?=[\x00-\x7f])(\C) |
	(?=[\x80-\x{7ff}])(\C)(\C) |
	(?=[\x{800}-\x{ffff}])(\C)(\C)(\C) |
	(?=[\x{10000}-\x{1fffff}])(\C)(\C)(\C)(\C))

[aeiou] [^aeiou] [d-m]
[W-]46] [W-\]46]
[z-\xff]
[A-\d] [A-[:digit:]]
[\000-\037]
(?i)[W-c] [][\\^_`wxyzabc]
[\xc8-\xcb]
# If a closing square bracket is required as a member of the class, it should be the first data character in the class
# (after an initial circumflex, if present) or escaped with a backslash.
[]\\^_`wxyzabc]

[01[:alpha:]%]
[12[:^digit:]]

[[:<:]]  is converted to  \b(?=\w)
[[:>:]]  is converted to  \b(?<=\w)
# Only these exact character sequences are recognized. A sequence such as
[a[:<:]b]
# provokes error for an unrecognized POSIX class name.

gilbert|sullivan
(a(?i)b)c
(a(?i)b|c)

(?i:saturday|sunday)
(?:(?i)saturday|sunday)

(?|(Sat)ur|(Sun))day
/(?|(abc)|(def))\1/
/(?|(abc)|(def))(?1)/

(?:(?<n>foo)|(?<n>bar))\k<n>
z{2,4}
[aeiou]{3,}
\d{8}
(a?)*
/\*.*\*/
/\*.*?\*/
\d??\d
(.*)abc\1
(?>.*?a)b
(tweedle[dume]{3}\s*)+
/(a|(b))+/
\d+foo
(?>\d+)foo
\d++foo
(abc|xyz){2,3}+
(\D+|<\d+>)*[!?]
((?>\D+)|<\d+>)*[!?]
(ring), \1
(ring), \g1
(ring), \g{1}
(abc(def)ghi)\g{-1}
(sens|respons)e and \1ibility
((?i)rah)\s+\1
(?<p1>(?i)rah)\s+\k<p1>
(?'p1'(?i)rah)\s+\k{p1}
(?P<p1>(?i)rah)\s+(?P=p1)
(?<p1>(?i)rah)\s+\g{p1}
(a|(bc))\2
(a\1)
(a|b\1)+
\w+(?=;)
foo(?!bar)
(?!foo)bar
(?<!foo)bar
(?<=bullock|donkey)
(?<!dogs?|cats?)
(?<=ab(c|de))
(?<=abc|abde)
abcd$
^.*abcd$
^.*+(?<=abcd)
(?<=\d{3})(?<!999)foo
(?<=\d{3}...)(?<!999)foo
(?<=(?<!foo)bar)baz
(?<=\d{3}(?!999)...)foo

(?(condition)yes-pattern)
(?(condition)yes-pattern|no-pattern)

(?(1) (A|B|C) | (D | (?(2)E|F) | E) )

( $ )?    [^()]+    (?(1) $ )

( $ )?    [^()]+    (?(-1) $ )

(?<OPEN> $ )?    [^()]+    (?(<OPEN>) $ )

(?(R3)...) or (?(R&name)...)

(?(DEFINE) (?<byte> 2[0-4]\d | 25[0-5] | 1\d\d | [1-9]?\d) )
\b (?&byte) (\.(?&byte)){3} \b

(?(?=[^a-z]*[a-z])
\d{2}-[a-z]{3}-\d{2}  |  \d{2}-\d{2}-\d{2} )

abc #comment \n still comment
( $ ( [^()]++ | (?1) )* $ )
(?<pn> $ ( [^()]++ | (?&pn) )* $ )
(ab(cd)ef)
< (?: (?(R) \d++  | [^<>]*+) | (?R)) * >
^(.|(.)(?1)\2)$
^((.)(?1)\2|.)$
^((.)(?1)\2|.?)$
^(?:((.)(?1)\2|)|((.)(?3)\4|.))
^\W*+(?:((.)\W*+(?1)\W*+\2|)|((.)\W*+(?3)\W*+\4|\W*+.\W*+))\W*+$
^(.)(\1|a(?2))

(...(absolute)...)...(?2)...
(...(relative)...)...(?-1)...
(...(?+1)...(relative)...)
(sens|respons)e and \1ibility
(sens|respons)e and (?1)ibility
(abc)(?i:(?-1))
(?<pn> $ ( (?>[^()]+) | \g<pn> )* $ )
(sens|respons)e and \g'1'ibility
(abc)(?i:\g<-1>)
(?C1)abc(?C2)def
# An explicit callout may also be set at this position, as in this example:
# Note that this applies only to assertion conditions, not to other types of condition.
(?(?C9)(?=a)abc|def)
A((?:A|B(*ACCEPT)|C)D)
a+(?C)(*FAIL)
/X(*MARK:A)Y|X(*MARK:B)Z/K
a+(*COMMIT)b
/(*COMMIT)abc/
a+(*SKIP)b
( COND1 (*THEN) FOO | COND2 (*THEN) BAR | COND3 (*THEN) BAZ ) ...
A (B(*THEN)C) | D
A (B(*THEN)C | (*FAIL)) | D
^.*? (?(?=a) a | b(*THEN)c )
(A(*COMMIT)B(*THEN)C|ABD)
...(*COMMIT)(*PRUNE)...
/(a(*COMMIT)b)+ac/

Other details

# Option setting: extended mode (x) is enabled by default
(?-i) (?-J) (?-m) (?-s) (?-U) (?-x) # This part is no longer in extended mode so this is not a comment
(?iJm) (?-iJm) (?iJm-sUx) (?xJm-s-U-i) # Back to extended mode: this is a comment

# Reset group numbers:
(?|(reset)|(group)|(numbers))

## Everything that can take a name:
# Capturing groups:
 (?<named>capturing_group)  (?<1badname>capturing_group)  (?<nametoolooooooooooooooooooooooooong>capturing_group)
(?P<named>capturing_group) (?P<2badname>capturing_group) (?P<nametoolooooooooooooooooooooooooong>capturing_group)
 (?'named'capturing_group)  (?'3badname'capturing_group)  (?'nametoolooooooooooooooooooooooooong'capturing_group)

# Backreferences:
 \g{name}  \g{1badname}  \g{nametoolooooooooooooooooooooooooong}
 \k{name}  \k{1badname}  \k{nametoolooooooooooooooooooooooooong}
 \k<name>  \k<1badname>  \k<nametoolooooooooooooooooooooooooong>
 \k'name'  \k'1badname'  \k'nametoolooooooooooooooooooooooooong'
(?P=name) (?P=1badname) (?P=nametoolooooooooooooooooooooooooong)

# Subroutines:
(?P>name) (?P>1badname) (?P>nametoolooooooooooooooooooooooooong)
 (?&name)  (?&1badname)  (?&nametoolooooooooooooooooooooooooong)
 \g<name>  \g<1badname>  \g<nametoolooooooooooooooooooooooooong>
 \g'name'  \g'1badname'  \g'nametoolooooooooooooooooooooooooong'

# Conditions:
 (?(<name>)...) (?(<1badname>)...) (?(<nametoolooooooooooooooooooooooooong>)...)
 (?('name')...) (?('1badname')...) (?('nametoolooooooooooooooooooooooooong')...)
  (?(name)...)   (?(1badname)...)   (?(nametoolooooooooooooooooooooooooong)...)
(?(R&name)...) (?(R&1badname)...) (?(R&nametoolooooooooooooooooooooooooong)...)

# Verbs:
     (*:name)      (*:1badname)      (*:nametoolooooooooooooooooooooooooong)
 (*MARK:name)  (*MARK:1badname)  (*MARK:nametoolooooooooooooooooooooooooong)
(*PRUNE:name) (*PRUNE:1badname) (*PRUNE:nametoolooooooooooooooooooooooooong)
 (*SKIP:name)  (*SKIP:1badname)  (*SKIP:nametoolooooooooooooooooooooooooong)
 (*THEN:name)  (*THEN:1badname)  (*THEN:nametoolooooooooooooooooooooooooong)

# Nested groups on a single line:
  (?<level1>  (?<level2>  (?<level3>  (?<level4>  (?<level5>  (?<level6>  (?<level7>  (?<level8>  8)  7)  6)  5)  4)  3)  2)  1)

# Nested groups on multiple lines:
	(?<level1>
		(?<level2>
			(?<level3>
				(?<level4>
					(?<level5>
						(?<level6>
							(?<level7>
								(?<level8>
									This ought to be enough for everyone ©
								)
							)
						)
					)
				)
			)
		)
	)

\[\\\#/\]       # [\#/] escaped

# Better \Q...\E test:
\Q Everything between \Q and \ E is escaped: !@#$%^&*()_-+[]{} \E

# \Q...\E in a character class:
[123\QYou can use \Q...\ E inside character classes\E456]

# It remains ugly in extended mode though:
\Q hello
   I span
   multiple lines
   and this is ugly
\E

# Octal notations:
\0 \07 \077 \123 \o{456}

# Hexadecimal notations:
\x \xa \xaa \xAA \x{bb} \u12ff

(?C) (?C0) (?C1) (?C23) (?C234) (?C255) (?C256) # callouts

\d \D \h \H \v \V \w \W
\n \N # LF (line feed, 0x0A) character vs any character that is not a newline

# More \p tests:
\p{C}   \P{C}   \p{^C}   \P{^C}
\p{L&}  \P{L&}  \p{^L&}  \P{^L&}
\p{Xwd} \P{Xwd} \p{^Xwd} \P{^Xwd}
\p{Han} \P{Han} \p{^Han} \P{^Han}
\p{Hna} \P{Hna} \p{^Hna} \P{^Hna} # The Han/Hna typo is made visible

# POSIX named classes are supported only within a class:
[:word:] [:^space:]
[
	[:alnum:]  [:alpha:]  [:ascii:]  [:blank:]   [:cntrl:]
	[:digit:]  [:graph:]  [:lower:]  [:print:]   [:punct:]
	[:space:]  [:upper:]  [:word:]   [:xdigit:]  [:fake:]
	[:^alnum:] [:^alpha:] [:^ascii:] [:^blank:]  [:^cntrl:]
	[:^digit:] [:^graph:] [:^lower:] [:^print:]  [:^punct:]
	[:^space:] [:^upper:] [:^word:]  [:^xdigit:] [:^fake:]
]

# Quantifiers: there are no {,m} quantifiers:
x{,6}      # For example, {,6} is not  a  quantifier, but a literal string of four characters.

# Conditional patterns: DEFINE should not prevent names starting with "DEFINE"
(?(DEFINER)yes-pattern|no-pattern)