4 perlrecharclass - Perl Regular Expression Character Classes
8 The top level documentation about Perl regular expressions
11 This manual page discusses the syntax and use of character
12 classes in Perl regular expressions.
14 A character class is a way of denoting a set of characters
15 in such a way that one character of the set is matched.
16 It's important to remember that: matching a character class
17 consumes exactly one character in the source string. (The source
18 string is the string the regular expression is matched against.)
20 There are three types of character classes in Perl regular
21 expressions: the dot, backslash sequences, and the form enclosed in square
22 brackets. Keep in mind, though, that often the term "character class" is used
23 to mean just the bracketed form. Certainly, most Perl documentation does that.
27 The dot (or period), C<.> is probably the most used, and certainly
28 the most well-known character class. By default, a dot matches any
29 character, except for the newline. That default can be changed to
30 add matching the newline by using the I<single line> modifier:
31 for the entire regular expression with the C</s> modifier, or
32 locally with C<(?s)> (and even globally within the scope of
33 L<C<use re '/s'>|re/'E<sol>flags' mode>). (The C<L</\N>> backslash
35 below, matches any character except newline without regard to the
36 I<single line> modifier.)
38 Here are some examples:
42 "" =~ /./ # No match (dot has to match a character)
43 "\n" =~ /./ # No match (dot does not match a newline)
44 "\n" =~ /./s # Match (global 'single line' modifier)
45 "\n" =~ /(?s:.)/ # Match (local 'single line' modifier)
46 "ab" =~ /^.$/ # No match (dot matches one character)
48 =head2 Backslash sequences
49 X<\w> X<\W> X<\s> X<\S> X<\d> X<\D> X<\p> X<\P>
50 X<\N> X<\v> X<\V> X<\h> X<\H>
53 A backslash sequence is a sequence of characters, the first one of which is a
54 backslash. Perl ascribes special meaning to many such sequences, and some of
55 these are character classes. That is, they match a single character each,
56 provided that the character belongs to the specific set of characters defined
59 Here's a list of the backslash sequences that are character classes. They
60 are discussed in more detail below. (For the backslash sequences that aren't
61 character classes, see L<perlrebackslash>.)
63 \d Match a decimal digit character.
64 \D Match a non-decimal-digit character.
65 \w Match a "word" character.
66 \W Match a non-"word" character.
67 \s Match a whitespace character.
68 \S Match a non-whitespace character.
69 \h Match a horizontal whitespace character.
70 \H Match a character that isn't horizontal whitespace.
71 \v Match a vertical whitespace character.
72 \V Match a character that isn't vertical whitespace.
73 \N Match a character that isn't a newline.
74 \pP, \p{Prop} Match a character that has the given Unicode property.
75 \PP, \P{Prop} Match a character that doesn't have the Unicode property
79 C<\N>, available starting in v5.12, like the dot, matches any
80 character that is not a newline. The difference is that C<\N> is not influenced
81 by the I<single line> regular expression modifier (see L</The dot> above). Note
82 that the form C<\N{...}> may mean something completely different. When the
83 C<{...}> is a L<quantifier|perlre/Quantifiers>, it means to match a non-newline
84 character that many times. For example, C<\N{3}> means to match 3
85 non-newlines; C<\N{5,}> means to match 5 or more non-newlines. But if C<{...}>
86 is not a legal quantifier, it is presumed to be a named character. See
87 L<charnames> for those. For example, none of C<\N{COLON}>, C<\N{4F}>, and
88 C<\N{F4}> contain legal quantifiers, so Perl will try to find characters whose
89 names are respectively C<COLON>, C<4F>, and C<F4>.
93 C<\d> matches a single character considered to be a decimal I<digit>.
94 If the C</a> regular expression modifier is in effect, it matches [0-9].
96 matches anything that is matched by C<\p{Digit}>, which includes [0-9].
97 (An unlikely possible exception is that under locale matching rules, the
98 current locale might not have C<[0-9]> matched by C<\d>, and/or might match
99 other characters whose code point is less than 256. The only such locale
100 definitions that are legal would be to match C<[0-9]> plus another set of
101 10 consecutive digit characters; anything else would be in violation of
102 the C language standard, but Perl doesn't currently assume anything in
105 What this means is that unless the C</a> modifier is in effect C<\d> not
106 only matches the digits '0' - '9', but also Arabic, Devanagari, and
107 digits from other languages. This may cause some confusion, and some
110 Some digits that C<\d> matches look like some of the [0-9] ones, but
111 have different values. For example, BENGALI DIGIT FOUR (U+09EA) looks
112 very much like an ASCII DIGIT EIGHT (U+0038), and LEPCHA DIGIT SIX
113 (U+1C46) looks very much like an ASCII DIGIT FIVE (U+0035). An
115 is expecting only the ASCII digits might be misled, or if the match is
116 C<\d+>, the matched string might contain a mixture of digits from
117 different writing systems that look like they signify a number different
118 than they actually do. L<Unicode::UCD/num()> can
120 calculate the value, returning C<undef> if the input string contains
121 such a mixture. Otherwise, for example, a displayed price might be
122 deliberately different than it appears.
124 What C<\p{Digit}> means (and hence C<\d> except under the C</a>
125 modifier) is C<\p{General_Category=Decimal_Number}>, or synonymously,
126 C<\p{General_Category=Digit}>. Starting with Unicode version 4.1, this
127 is the same set of characters matched by C<\p{Numeric_Type=Decimal}>.
128 But Unicode also has a different property with a similar name,
129 C<\p{Numeric_Type=Digit}>, which matches a completely different set of
130 characters. These characters are things such as C<CIRCLED DIGIT ONE>
131 or subscripts, or are from writing systems that lack all ten digits.
133 The design intent is for C<\d> to exactly match the set of characters
134 that can safely be used with "normal" big-endian positional decimal
135 syntax, where, for example 123 means one 'hundred', plus two 'tens',
136 plus three 'ones'. This positional notation does not necessarily apply
137 to characters that match the other type of "digit",
138 C<\p{Numeric_Type=Digit}>, and so C<\d> doesn't match them.
140 The Tamil digits (U+0BE6 - U+0BEF) can also legally be
141 used in old-style Tamil numbers in which they would appear no more than
142 one in a row, separated by characters that mean "times 10", "times 100",
143 etc. (See L<https://www.unicode.org/notes/tn21>.)
145 Any character not matched by C<\d> is matched by C<\D>.
147 =head3 Word characters
149 A C<\w> matches a single alphanumeric character (an alphabetic character, or a
150 decimal digit); or a connecting punctuation character, such as an
151 underscore ("_"); or a "mark" character (like some sort of accent) that
152 attaches to one of those. It does not match a whole word. To match a
153 whole word, use C<\w+>. This isn't the same thing as matching an
154 English word, but in the ASCII range it is the same as a string of
155 Perl-identifier characters.
159 =item If the C</a> modifier is in effect ...
161 C<\w> matches the 63 characters [a-zA-Z0-9_].
167 =item For code points above 255 ...
169 C<\w> matches the same as C<\p{Word}> matches in this range. That is,
170 it matches Thai letters, Greek letters, etc. This includes connector
171 punctuation (like the underscore) which connect two words together, or
172 diacritics, such as a C<COMBINING TILDE> and the modifier letters, which
173 are generally used to add auxiliary markings to letters.
175 =item For code points below 256 ...
179 =item if locale rules are in effect ...
181 C<\w> matches the platform's native underscore character plus whatever
182 the locale considers to be alphanumeric.
184 =item if, instead, Unicode rules are in effect ...
186 C<\w> matches exactly what C<\p{Word}> matches.
190 C<\w> matches [a-zA-Z0-9_].
198 Which rules apply are determined as described in L<perlre/Which character set modifier is in effect?>.
200 There are a number of security issues with the full Unicode list of word
201 characters. See L<http://unicode.org/reports/tr36>.
203 Also, for a somewhat finer-grained set of characters that are in programming
204 language identifiers beyond the ASCII range, you may wish to instead use the
205 more customized L</Unicode Properties>, C<\p{ID_Start}>,
206 C<\p{ID_Continue}>, C<\p{XID_Start}>, and C<\p{XID_Continue}>. See
207 L<http://unicode.org/reports/tr31>.
209 Any character not matched by C<\w> is matched by C<\W>.
213 C<\s> matches any single character considered whitespace.
217 =item If the C</a> modifier is in effect ...
219 In all Perl versions, C<\s> matches the 5 characters [\t\n\f\r ]; that
220 is, the horizontal tab,
221 the newline, the form feed, the carriage return, and the space.
222 Starting in Perl v5.18, it also matches the vertical tab, C<\cK>.
223 See note C<[1]> below for a discussion of this.
229 =item For code points above 255 ...
231 C<\s> matches exactly the code points above 255 shown with an "s" column
234 =item For code points below 256 ...
238 =item if locale rules are in effect ...
240 C<\s> matches whatever the locale considers to be whitespace.
242 =item if, instead, Unicode rules are in effect ...
244 C<\s> matches exactly the characters shown with an "s" column in the
249 C<\s> matches [\t\n\f\r ] and, starting in Perl
250 v5.18, the vertical tab, C<\cK>.
251 (See note C<[1]> below for a discussion of this.)
252 Note that this list doesn't include the non-breaking space.
260 Which rules apply are determined as described in L<perlre/Which character set modifier is in effect?>.
262 Any character not matched by C<\s> is matched by C<\S>.
264 C<\h> matches any character considered horizontal whitespace;
265 this includes the platform's space and tab characters and several others
266 listed in the table below. C<\H> matches any character
267 not considered horizontal whitespace. They use the platform's native
268 character set, and do not consider any locale that may otherwise be in
271 C<\v> matches any character considered vertical whitespace;
272 this includes the platform's carriage return and line feed characters (newline)
273 plus several other characters, all listed in the table below.
274 C<\V> matches any character not considered vertical whitespace.
275 They use the platform's native character set, and do not consider any
276 locale that may otherwise be in use.
278 C<\R> matches anything that can be considered a newline under Unicode
279 rules. It can match a multi-character sequence. It cannot be used inside
280 a bracketed character class; use C<\v> instead (vertical whitespace).
281 It uses the platform's
282 native character set, and does not consider any locale that may
284 Details are discussed in L<perlrebackslash>.
286 Note that unlike C<\s> (and C<\d> and C<\w>), C<\h> and C<\v> always match
287 the same characters, without regard to other factors, such as the active
288 locale or whether the source string is in UTF-8 format.
290 One might think that C<\s> is equivalent to C<[\h\v]>. This is indeed true
291 starting in Perl v5.18, but prior to that, the sole difference was that the
292 vertical tab (C<"\cK">) was not matched by C<\s>.
294 The following table is a complete listing of characters matched by
295 C<\s>, C<\h> and C<\v> as of Unicode 14.0.
297 The first column gives the Unicode code point of the character (in hex format),
298 the second column gives the (Unicode) name. The third column indicates
299 by which class(es) the character is matched (assuming no locale is in
300 effect that changes the C<\s> matching).
302 0x0009 CHARACTER TABULATION h s
303 0x000a LINE FEED (LF) vs
304 0x000b LINE TABULATION vs [1]
305 0x000c FORM FEED (FF) vs
306 0x000d CARRIAGE RETURN (CR) vs
308 0x0085 NEXT LINE (NEL) vs [2]
309 0x00a0 NO-BREAK SPACE h s [2]
310 0x1680 OGHAM SPACE MARK h s
315 0x2004 THREE-PER-EM SPACE h s
316 0x2005 FOUR-PER-EM SPACE h s
317 0x2006 SIX-PER-EM SPACE h s
318 0x2007 FIGURE SPACE h s
319 0x2008 PUNCTUATION SPACE h s
320 0x2009 THIN SPACE h s
321 0x200a HAIR SPACE h s
322 0x2028 LINE SEPARATOR vs
323 0x2029 PARAGRAPH SEPARATOR vs
324 0x202f NARROW NO-BREAK SPACE h s
325 0x205f MEDIUM MATHEMATICAL SPACE h s
326 0x3000 IDEOGRAPHIC SPACE h s
332 Prior to Perl v5.18, C<\s> did not match the vertical tab.
333 C<[^\S\cK]> (obscurely) matches what C<\s> traditionally did.
337 NEXT LINE and NO-BREAK SPACE may or may not match C<\s> depending
338 on the rules in effect. See
339 L<the beginning of this section|/Whitespace>.
343 =head3 Unicode Properties
345 C<\pP> and C<\p{Prop}> are character classes to match characters that fit given
346 Unicode properties. One letter property names can be used in the C<\pP> form,
347 with the property name following the C<\p>, otherwise, braces are required.
348 When using braces, there is a single form, which is just the property name
349 enclosed in the braces, and a compound form which looks like C<\p{name=value}>,
350 which means to match if the property "name" for the character has that particular
352 For instance, a match for a number can be written as C</\pN/> or as
353 C</\p{Number}/>, or as C</\p{Number=True}/>.
354 Lowercase letters are matched by the property I<Lowercase_Letter> which
355 has the short form I<Ll>. They need the braces, so are written as C</\p{Ll}/> or
356 C</\p{Lowercase_Letter}/>, or C</\p{General_Category=Lowercase_Letter}/>
357 (the underscores are optional).
358 C</\pLl/> is valid, but means something different.
359 It matches a two character string: a letter (Unicode property C<\pL>),
360 followed by a lowercase C<l>.
362 What a Unicode property matches is never subject to locale rules, and
363 if locale rules are not otherwise in effect, the use of a Unicode
364 property will force the regular expression into using Unicode rules, if
367 Note that almost all properties are immune to case-insensitive matching.
368 That is, adding a C</i> regular expression modifier does not change what
369 they match. But there are two sets that are affected. The first set is
372 and C<Titlecase_Letter>,
373 all of which match C<Cased_Letter> under C</i> matching.
378 all of which match C<Cased> under C</i> matching.
379 (The difference between these sets is that some things, such as Roman
380 numerals, come in both upper and lower case, so they are C<Cased>, but
381 aren't considered to be letters, so they aren't C<Cased_Letter>s. They're
382 actually C<Letter_Number>s.)
383 This set also includes its subsets C<PosixUpper> and C<PosixLower>, both
384 of which under C</i> match C<PosixAlpha>.
386 For more details on Unicode properties, see L<perlunicode/Unicode
387 Character Properties>; for a
388 complete list of possible properties, see
389 L<perluniprops/Properties accessible through \p{} and \P{}>,
390 which notes all forms that have C</i> differences.
391 It is also possible to define your own properties. This is discussed in
392 L<perlunicode/User-Defined Character Properties>.
394 Unicode properties are defined (surprise!) only on Unicode code points.
395 Starting in v5.20, when matching against C<\p> and C<\P>, Perl treats
396 non-Unicode code points (those above the legal Unicode maximum of
397 0x10FFFF) as if they were typical unassigned Unicode code points.
399 Prior to v5.20, Perl raised a warning and made all matches fail on
400 non-Unicode code points. This could be somewhat surprising:
402 chr(0x110000) =~ \p{ASCII_Hex_Digit=True} # Fails on Perls < v5.20.
403 chr(0x110000) =~ \p{ASCII_Hex_Digit=False} # Also fails on Perls
406 Even though these two matches might be thought of as complements, until
407 v5.20 they were so only on Unicode code points.
409 Starting in perl v5.30, wildcards are allowed in Unicode property
410 values. See L<perlunicode/Wildcards in Property Values>.
414 "a" =~ /\w/ # Match, "a" is a 'word' character.
415 "7" =~ /\w/ # Match, "7" is a 'word' character as well.
416 "a" =~ /\d/ # No match, "a" isn't a digit.
417 "7" =~ /\d/ # Match, "7" is a digit.
418 " " =~ /\s/ # Match, a space is whitespace.
419 "a" =~ /\D/ # Match, "a" is a non-digit.
420 "7" =~ /\D/ # No match, "7" is not a non-digit.
421 " " =~ /\S/ # No match, a space is not non-whitespace.
423 " " =~ /\h/ # Match, space is horizontal whitespace.
424 " " =~ /\v/ # No match, space is not vertical whitespace.
425 "\r" =~ /\v/ # Match, a return is vertical whitespace.
427 "a" =~ /\pL/ # Match, "a" is a letter.
428 "a" =~ /\p{Lu}/ # No match, /\p{Lu}/ matches upper case letters.
430 "\x{0e0b}" =~ /\p{Thai}/ # Match, \x{0e0b} is the character
431 # 'THAI CHARACTER SO SO', and that's in
432 # Thai Unicode class.
433 "a" =~ /\P{Lao}/ # Match, as "a" is not a Laotian character.
435 It is worth emphasizing that C<\d>, C<\w>, etc, match single characters, not
436 complete numbers or words. To match a number (that consists of digits),
437 use C<\d+>; to match a word, use C<\w+>. But be aware of the security
438 considerations in doing so, as mentioned above.
440 =head2 Bracketed Character Classes
442 The third form of character class you can use in Perl regular expressions
443 is the bracketed character class. In its simplest form, it lists the characters
444 that may be matched, surrounded by square brackets, like this: C<[aeiou]>.
445 This matches one of C<a>, C<e>, C<i>, C<o> or C<u>. Like the other
446 character classes, exactly one character is matched.* To match
447 a longer string consisting of characters mentioned in the character
448 class, follow the character class with a L<quantifier|perlre/Quantifiers>. For
449 instance, C<[aeiou]+> matches one or more lowercase English vowels.
451 Repeating a character in a character class has no
452 effect; it's considered to be in the set only once.
456 "e" =~ /[aeiou]/ # Match, as "e" is listed in the class.
457 "p" =~ /[aeiou]/ # No match, "p" is not listed in the class.
458 "ae" =~ /^[aeiou]$/ # No match, a character class only matches
459 # a single character.
460 "ae" =~ /^[aeiou]+$/ # Match, due to the quantifier.
464 * There are two exceptions to a bracketed character class matching a
465 single character only. Each requires special handling by Perl to make
472 When the class is to match caselessly under C</i> matching rules, and a
473 character that is explicitly mentioned inside the class matches a
474 multiple-character sequence caselessly under Unicode rules, the class
475 will also match that sequence. For example, Unicode says that the
476 letter C<LATIN SMALL LETTER SHARP S> should match the sequence C<ss>
477 under C</i> rules. Thus,
479 'ss' =~ /\A\N{LATIN SMALL LETTER SHARP S}\z/i # Matches
480 'ss' =~ /\A[aeioust\N{LATIN SMALL LETTER SHARP S}]\z/i # Matches
482 For this to happen, the class must not be inverted (see L</Negation>)
483 and the character must be explicitly specified, and not be part of a
484 multi-character range (not even as one of its endpoints). (L</Character
485 Ranges> will be explained shortly.) Therefore,
487 'ss' =~ /\A[\0-\x{ff}]\z/ui # Doesn't match
488 'ss' =~ /\A[\0-\N{LATIN SMALL LETTER SHARP S}]\z/ui # No match
489 'ss' =~ /\A[\xDF-\xDF]\z/ui # Matches on ASCII platforms, since
490 # \xDF is LATIN SMALL LETTER SHARP S,
491 # and the range is just a single
494 Note that it isn't a good idea to specify these types of ranges anyway.
498 Some names known to C<\N{...}> refer to a sequence of multiple characters,
499 instead of the usual single character. When one of these is included in
500 the class, the entire sequence is matched. For example,
502 "\N{TAMIL LETTER KA}\N{TAMIL VOWEL SIGN AU}"
503 =~ / ^ [\N{TAMIL SYLLABLE KAU}] $ /x;
505 matches, because C<\N{TAMIL SYLLABLE KAU}> is a named sequence
506 consisting of the two characters matched against. Like the other
507 instance where a bracketed class can match multiple characters, and for
508 similar reasons, the class must not be inverted, and the named sequence
509 may not appear in a range, even one where it is both endpoints. If
510 these happen, it is a fatal error if the character class is within the
511 scope of L<C<use re 'strict>|re/'strict' mode>, or within an extended
512 L<C<(?[...])>|/Extended Bracketed Character Classes> class; otherwise
513 only the first code point is used (with a C<regexp>-type warning
518 =head3 Special Characters Inside a Bracketed Character Class
520 Most characters that are meta characters in regular expressions (that
521 is, characters that carry a special meaning like C<.>, C<*>, or C<(>) lose
522 their special meaning and can be used inside a character class without
523 the need to escape them. For instance, C<[()]> matches either an opening
524 parenthesis, or a closing parenthesis, and the parens inside the character
525 class don't group or capture. Be aware that, unless the pattern is
526 evaluated in single-quotish context, variable interpolation will take
527 place before the bracketed class is parsed:
530 $a =~ m'[$,]'; # single-quotish: matches '$' or ','
531 $a =~ q{[$,]}' # same
532 $a =~ m/[$,]/; # double-quotish: Because we made an
533 # assignment to $, above, this now
534 # matches "\t", "|", or " "
536 Characters that may carry a special meaning inside a character class are:
537 C<\>, C<^>, C<->, C<[> and C<]>, and are discussed below. They can be
538 escaped with a backslash, although this is sometimes not needed, in which
539 case the backslash may be omitted.
541 The sequence C<\b> is special inside a bracketed character class. While
542 outside the character class, C<\b> is an assertion indicating a point
543 that does not have either two word characters or two non-word characters
544 on either side, inside a bracketed character class, C<\b> matches a
554 C<\N{U+I<hex char>}>,
559 are also special and have the same meanings as they do outside a
560 bracketed character class.
562 Also, a backslash followed by two or three octal digits is considered an octal
565 A C<[> is not special inside a character class, unless it's the start of a
566 POSIX character class (see L</POSIX Character Classes> below). It normally does
569 A C<]> is normally either the end of a POSIX character class (see
570 L</POSIX Character Classes> below), or it signals the end of the bracketed
571 character class. If you want to include a C<]> in the set of characters, you
572 must generally escape it.
574 However, if the C<]> is the I<first> (or the second if the first
575 character is a caret) character of a bracketed character class, it
576 does not denote the end of the class (as you cannot have an empty class)
577 and is considered part of the set of characters that can be matched without
582 "+" =~ /[+?*]/ # Match, "+" in a character class is not special.
583 "\cH" =~ /[\b]/ # Match, \b inside in a character class
584 # is equivalent to a backspace.
585 "]" =~ /[][]/ # Match, as the character class contains
587 "[]" =~ /[[]]/ # Match, the pattern contains a character class
588 # containing just [, and the character class is
591 =head3 Bracketed Character Classes and the C</xx> pattern modifier
593 Normally SPACE and TAB characters have no special meaning inside a
594 bracketed character class; they are just added to the list of characters
595 matched by the class. But if the L<C</xx>|perlre/E<sol>x and E<sol>xx>
596 pattern modifier is in effect, they are generally ignored and can be
597 added to improve readability. They can't be added in the middle of a
600 / [ \x{10 FFFF} ] /xx # WRONG!
602 The SPACE in the middle of the hex constant is illegal.
604 To specify a literal SPACE character, you can escape it with a
609 This matches the English vowels plus the SPACE character.
611 For clarity, you should already have been using C<\t> to specify a
612 literal tab, and C<\t> is unaffected by C</xx>.
614 =head3 Character Ranges
616 It is not uncommon to want to match a range of characters. Luckily, instead
617 of listing all characters in the range, one may use the hyphen (C<->).
618 If inside a bracketed character class you have two characters separated
619 by a hyphen, it's treated as if all characters between the two were in
620 the class. For instance, C<[0-9]> matches any ASCII digit, and C<[a-m]>
621 matches any lowercase letter from the first half of the ASCII alphabet.
623 Note that the two characters on either side of the hyphen are not
624 necessarily both letters or both digits. Any character is possible,
625 although not advisable. C<['-?]> contains a range of characters, but
626 most people will not know which characters that means. Furthermore,
627 such ranges may lead to portability problems if the code has to run on
628 a platform that uses a different character set, such as EBCDIC.
630 If a hyphen in a character class cannot syntactically be part of a range, for
631 instance because it is the first or the last character of the character class,
632 or if it immediately follows a range, the hyphen isn't special, and so is
633 considered a character to be matched literally. If you want a hyphen in
634 your set of characters to be matched and its position in the class is such
635 that it could be considered part of a range, you must escape that hyphen
640 [a-z] # Matches a character that is a lower case ASCII letter.
641 [a-fz] # Matches any letter between 'a' and 'f' (inclusive) or
643 [-z] # Matches either a hyphen ('-') or the letter 'z'.
644 [a-f-m] # Matches any letter between 'a' and 'f' (inclusive), the
645 # hyphen ('-'), or the letter 'm'.
646 ['-?] # Matches any of the characters '()*+,-./0123456789:;<=>?
647 # (But not on an EBCDIC platform).
648 [\N{APOSTROPHE}-\N{QUESTION MARK}]
649 # Matches any of the characters '()*+,-./0123456789:;<=>?
650 # even on an EBCDIC platform.
651 [\N{U+27}-\N{U+3F}] # Same. (U+27 is "'", and U+3F is "?")
653 As the final two examples above show, you can achieve portability to
654 non-ASCII platforms by using the C<\N{...}> form for the range
655 endpoints. These indicate that the specified range is to be interpreted
656 using Unicode values, so C<[\N{U+27}-\N{U+3F}]> means to match
657 C<\N{U+27}>, C<\N{U+28}>, C<\N{U+29}>, ..., C<\N{U+3D}>, C<\N{U+3E}>,
658 and C<\N{U+3F}>, whatever the native code point versions for those are.
659 These are called "Unicode" ranges. If either end is of the C<\N{...}>
660 form, the range is considered Unicode. A C<regexp> warning is raised
661 under C<S<"use re 'strict'">> if the other endpoint is specified
664 [\N{U+00}-\x09] # Warning under re 'strict'; \x09 is non-portable
665 [\N{U+00}-\t] # No warning;
667 Both of the above match the characters C<\N{U+00}> C<\N{U+01}>, ...
668 C<\N{U+08}>, C<\N{U+09}>, but the C<\x09> looks like it could be a
669 mistake so the warning is raised (under C<re 'strict'>) for it.
671 Perl also guarantees that the ranges C<A-Z>, C<a-z>, C<0-9>, and any
672 subranges of these match what an English-only speaker would expect them
673 to match on any platform. That is, C<[A-Z]> matches the 26 ASCII
675 C<[a-z]> matches the 26 lowercase letters; and C<[0-9]> matches the 10
676 digits. Subranges, like C<[h-k]>, match correspondingly, in this case
677 just the four letters C<"h">, C<"i">, C<"j">, and C<"k">. This is the
678 natural behavior on ASCII platforms where the code points (ordinal
679 values) for C<"h"> through C<"k"> are consecutive integers (0x68 through
680 0x6B). But special handling to achieve this may be needed on platforms
681 with a non-ASCII native character set. For example, on EBCDIC
682 platforms, the code point for C<"h"> is 0x88, C<"i"> is 0x89, C<"j"> is
683 0x91, and C<"k"> is 0x92. Perl specially treats C<[h-k]> to exclude the
684 seven code points in the gap: 0x8A through 0x90. This special handling is
685 only invoked when the range is a subrange of one of the ASCII uppercase,
686 lowercase, and digit ranges, AND each end of the range is expressed
687 either as a literal, like C<"A">, or as a named character (C<\N{...}>,
688 including the C<\N{U+...> form).
692 [i-j] # Matches either "i" or "j"
693 [i-\N{LATIN SMALL LETTER J}] # Same
695 [\N{U+69}-\N{U+6A}] # Same
696 [\x{89}-\x{91}] # Matches 0x89 ("i"), 0x8A .. 0x90, 0x91 ("j")
699 [i-J] # Matches, 0x89 ("i") .. 0xC1 ("J"); special
700 # handling doesn't apply because range is mixed
705 It is also possible to instead list the characters you do not want to
706 match. You can do so by using a caret (C<^>) as the first character in the
707 character class. For instance, C<[^a-z]> matches any character that is not a
708 lowercase ASCII letter, which therefore includes more than a million
709 Unicode code points. The class is said to be "negated" or "inverted".
711 This syntax make the caret a special character inside a bracketed character
712 class, but only if it is the first character of the class. So if you want
713 the caret as one of the characters to match, either escape the caret or
714 else don't list it first.
716 In inverted bracketed character classes, Perl ignores the Unicode rules
717 that normally say that named sequence, and certain characters should
718 match a sequence of multiple characters use under caseless C</i>
719 matching. Following those rules could lead to highly confusing
722 "ss" =~ /^[^\xDF]+$/ui; # Matches!
724 This should match any sequences of characters that aren't C<\xDF> nor
725 what C<\xDF> matches under C</i>. C<"s"> isn't C<\xDF>, but Unicode
726 says that C<"ss"> is what C<\xDF> matches under C</i>. So which one
727 "wins"? Do you fail the match because the string has C<ss> or accept it
728 because it has an C<s> followed by another C<s>? Perl has chosen the
729 latter. (See note in L</Bracketed Character Classes> above.)
733 "e" =~ /[^aeiou]/ # No match, the 'e' is listed.
734 "x" =~ /[^aeiou]/ # Match, as 'x' isn't a lowercase vowel.
735 "^" =~ /[^^]/ # No match, matches anything that isn't a caret.
736 "^" =~ /[x^]/ # Match, caret is not special here.
738 =head3 Backslash Sequences
740 You can put any backslash sequence character class (with the exception of
741 C<\N> and C<\R>) inside a bracketed character class, and it will act just
742 as if you had put all characters matched by the backslash sequence inside the
743 character class. For instance, C<[a-f\d]> matches any decimal digit, or any
744 of the lowercase letters between 'a' and 'f' inclusive.
746 C<\N> within a bracketed character class must be of the forms C<\N{I<name>}>
747 or C<\N{U+I<hex char>}>, and NOT be the form that matches non-newlines,
748 for the same reason that a dot C<.> inside a bracketed character class loses
749 its special meaning: it matches nearly anything, which generally isn't what you
755 /[\p{Thai}\d]/ # Matches a character that is either a Thai
756 # character, or a digit.
757 /[^\p{Arabic}()]/ # Matches a character that is neither an Arabic
758 # character, nor a parenthesis.
760 Backslash sequence character classes cannot form one of the endpoints
761 of a range. Thus, you can't say:
763 /[\p{Thai}-\d]/ # Wrong!
765 =head3 POSIX Character Classes
766 X<character class> X<\p> X<\p{}>
767 X<alpha> X<alnum> X<ascii> X<blank> X<cntrl> X<digit> X<graph>
768 X<lower> X<print> X<punct> X<space> X<upper> X<word> X<xdigit>
770 POSIX character classes have the form C<[:class:]>, where I<class> is the
771 name, and the C<[:> and C<:]> delimiters. POSIX character classes only appear
772 I<inside> bracketed character classes, and are a convenient and descriptive
773 way of listing a group of characters.
775 Be careful about the syntax,
778 $string =~ /[[:alpha:]]/
780 # Incorrect (will warn):
781 $string =~ /[:alpha:]/
783 The latter pattern would be a character class consisting of a colon,
784 and the letters C<a>, C<l>, C<p> and C<h>.
786 POSIX character classes can be part of a larger bracketed character class.
791 is valid and matches '0', '1', any alphabetic character, and the percent sign.
793 Perl recognizes the following POSIX character classes:
795 alpha Any alphabetical character (e.g., [A-Za-z]).
796 alnum Any alphanumeric character (e.g., [A-Za-z0-9]).
797 ascii Any character in the ASCII character set.
798 blank A GNU extension, equal to a space or a horizontal tab ("\t").
799 cntrl Any control character. See Note [2] below.
800 digit Any decimal digit (e.g., [0-9]), equivalent to "\d".
801 graph Any printable character, excluding a space. See Note [3] below.
802 lower Any lowercase character (e.g., [a-z]).
803 print Any printable character, including a space. See Note [4] below.
804 punct Any graphical character excluding "word" characters. Note [5].
805 space Any whitespace character. "\s" including the vertical tab
807 upper Any uppercase character (e.g., [A-Z]).
808 word A Perl extension (e.g., [A-Za-z0-9_]), equivalent to "\w".
809 xdigit Any hexadecimal digit (e.g., [0-9a-fA-F]). Note [7].
811 Like the L<Unicode properties|/Unicode Properties>, most of the POSIX
812 properties match the same regardless of whether case-insensitive (C</i>)
813 matching is in effect or not. The two exceptions are C<[:upper:]> and
814 C<[:lower:]>. Under C</i>, they each match the union of C<[:upper:]> and
817 Most POSIX character classes have two Unicode-style C<\p> property
818 counterparts. (They are not official Unicode properties, but Perl extensions
819 derived from official Unicode properties.) The table below shows the relation
820 between POSIX character classes and these counterparts.
822 One counterpart, in the column labelled "ASCII-range Unicode" in
823 the table, matches only characters in the ASCII character set.
825 The other counterpart, in the column labelled "Full-range Unicode", matches any
826 appropriate characters in the full Unicode character set. For example,
827 C<\p{Alpha}> matches not just the ASCII alphabetic characters, but any
828 character in the entire Unicode character set considered alphabetic.
829 An entry in the column labelled "backslash sequence" is a (short)
832 [[:...:]] ASCII-range Full-range backslash Note
833 Unicode Unicode sequence
834 -----------------------------------------------------
835 alpha \p{PosixAlpha} \p{XPosixAlpha}
836 alnum \p{PosixAlnum} \p{XPosixAlnum}
838 blank \p{PosixBlank} \p{XPosixBlank} \h [1]
839 or \p{HorizSpace} [1]
840 cntrl \p{PosixCntrl} \p{XPosixCntrl} [2]
841 digit \p{PosixDigit} \p{XPosixDigit} \d
842 graph \p{PosixGraph} \p{XPosixGraph} [3]
843 lower \p{PosixLower} \p{XPosixLower}
844 print \p{PosixPrint} \p{XPosixPrint} [4]
845 punct \p{PosixPunct} \p{XPosixPunct} [5]
846 \p{PerlSpace} \p{XPerlSpace} \s [6]
847 space \p{PosixSpace} \p{XPosixSpace} [6]
848 upper \p{PosixUpper} \p{XPosixUpper}
849 word \p{PosixWord} \p{XPosixWord} \w
850 xdigit \p{PosixXDigit} \p{XPosixXDigit} [7]
856 C<\p{Blank}> and C<\p{HorizSpace}> are synonyms.
860 Control characters don't produce output as such, but instead usually control
861 the terminal somehow: for example, newline and backspace are control characters.
862 On ASCII platforms, in the ASCII range, characters whose code points are
863 between 0 and 31 inclusive, plus 127 (C<DEL>) are control characters; on
864 EBCDIC platforms, their counterparts are control characters.
868 Any character that is I<graphical>, that is, visible. This class consists
869 of all alphanumeric characters and all punctuation characters.
873 All printable characters, which is the set of all graphical characters
874 plus those whitespace characters which are not also controls.
878 C<\p{PosixPunct}> and C<[[:punct:]]> in the ASCII range match all
879 non-controls, non-alphanumeric, non-space characters:
880 C<[-!"#$%&'()*+,./:;<=E<gt>?@[\\\]^_`{|}~]> (although if a locale is in effect,
881 it could alter the behavior of C<[[:punct:]]>).
883 The similarly named property, C<\p{Punct}>, matches a somewhat different
884 set in the ASCII range, namely
885 C<[-!"#%&'()*,./:;?@[\\\]_{}]>. That is, it is missing the nine
886 characters C<[$+E<lt>=E<gt>^`|~]>.
887 This is because Unicode splits what POSIX considers to be punctuation into two
888 categories, Punctuation and Symbols.
890 C<\p{XPosixPunct}> and (under Unicode rules) C<[[:punct:]]>, match what
891 C<\p{PosixPunct}> matches in the ASCII range, plus what C<\p{Punct}>
892 matches. This is different than strictly matching according to
893 C<\p{Punct}>. Another way to say it is that
894 if Unicode rules are in effect, C<[[:punct:]]> matches all characters
895 that Unicode considers punctuation, plus all ASCII-range characters that
896 Unicode considers symbols.
900 C<\p{XPerlSpace}> and C<\p{Space}> match identically starting with Perl
901 v5.18. In earlier versions, these differ only in that in non-locale
902 matching, C<\p{XPerlSpace}> did not match the vertical tab, C<\cK>.
903 Same for the two ASCII-only range forms.
907 Unlike C<[[:digit:]]> which matches digits in many writing systems, such
908 as Thai and Devanagari, there are currently only two sets of hexadecimal
909 digits, and it is unlikely that more will be added. This is because you
910 not only need the ten digits, but also the six C<[A-F]> (and C<[a-f]>)
911 to correspond. That means only the Latin script is suitable for these,
912 and Unicode has only two sets of these, the familiar ASCII set, and the
913 fullwidth forms starting at U+FF10 (FULLWIDTH DIGIT ZERO).
917 There are various other synonyms that can be used besides the names
918 listed in the table. For example, C<\p{XPosixAlpha}> can be written as
919 C<\p{Alpha}>. All are listed in
920 L<perluniprops/Properties accessible through \p{} and \P{}>.
922 Both the C<\p> counterparts always assume Unicode rules are in effect.
923 On ASCII platforms, this means they assume that the code points from 128
924 to 255 are Latin-1, and that means that using them under locale rules is
925 unwise unless the locale is guaranteed to be Latin-1 or UTF-8. In contrast, the
926 POSIX character classes are useful under locale rules. They are
927 affected by the actual rules in effect, as follows:
931 =item If the C</a> modifier, is in effect ...
933 Each of the POSIX classes matches exactly the same as their ASCII-range
940 =item For code points above 255 ...
942 The POSIX class matches the same as its Full-range counterpart.
944 =item For code points below 256 ...
948 =item if locale rules are in effect ...
950 The POSIX class matches according to the locale, except:
956 also includes the platform's native underscore character, no matter what
961 on platforms that don't have the POSIX C<ascii> extension, this matches
962 just the platform's native ASCII-range characters.
966 on platforms that don't have the POSIX C<blank> extension, this matches
967 just the platform's native tab and space characters.
971 =item if, instead, Unicode rules are in effect ...
973 The POSIX class matches the same as the Full-range counterpart.
977 The POSIX class matches the same as the ASCII range counterpart.
985 Which rules apply are determined as described in
986 L<perlre/Which character set modifier is in effect?>.
988 =head4 Negation of POSIX character classes
989 X<character class, negation>
991 A Perl extension to the POSIX character class is the ability to
992 negate it. This is done by prefixing the class name with a caret (C<^>).
995 POSIX ASCII-range Full-range backslash
996 Unicode Unicode sequence
997 -----------------------------------------------------
998 [[:^digit:]] \P{PosixDigit} \P{XPosixDigit} \D
999 [[:^space:]] \P{PosixSpace} \P{XPosixSpace}
1000 \P{PerlSpace} \P{XPerlSpace} \S
1001 [[:^word:]] \P{PerlWord} \P{XPosixWord} \W
1003 The backslash sequence can mean either ASCII- or Full-range Unicode,
1004 depending on various factors as described in L<perlre/Which character set modifier is in effect?>.
1006 =head4 [= =] and [. .]
1008 Perl recognizes the POSIX character classes C<[=class=]> and
1009 C<[.class.]>, but does not (yet?) support them. Any attempt to use
1010 either construct raises an exception.
1014 /[[:digit:]]/ # Matches a character that is a digit.
1015 /[01[:lower:]]/ # Matches a character that is either a
1016 # lowercase letter, or '0' or '1'.
1017 /[[:digit:][:^xdigit:]]/ # Matches a character that can be anything
1018 # except the letters 'a' to 'f' and 'A' to
1019 # 'F'. This is because the main character
1020 # class is composed of two POSIX character
1021 # classes that are ORed together, one that
1022 # matches any digit, and the other that
1023 # matches anything that isn't a hex digit.
1024 # The OR adds the digits, leaving only the
1025 # letters 'a' to 'f' and 'A' to 'F' excluded.
1027 =head3 Extended Bracketed Character Classes
1031 This is a fancy bracketed character class that can be used for more
1032 readable and less error-prone classes, and to perform set operations,
1033 such as intersection. An example is
1035 /(?[ \p{Thai} & \p{Digit} ])/
1037 This will match all the digit characters that are in the Thai script.
1039 This is an experimental feature available starting in 5.18, and is
1040 subject to change as we gain field experience with it. Any attempt to
1041 use it will raise a warning, unless disabled via
1043 no warnings "experimental::regex_sets";
1045 Comments on this feature are welcome; send email to
1046 C<perl5-porters@perl.org>.
1048 The rules used by L<C<use re 'strict>|re/'strict' mode> apply to this
1051 We can extend the example above:
1053 /(?[ ( \p{Thai} + \p{Lao} ) & \p{Digit} ])/
1055 This matches digits that are in either the Thai or Laotian scripts.
1057 Notice the white space in these examples. This construct always has
1058 the C<E<sol>xx> modifier turned on within it.
1060 The available binary operators are:
1064 | another name for '+', hence means union
1065 - subtraction (the result matches the set consisting of those
1066 code points matched by the first operand, excluding any that
1067 are also matched by the second operand)
1068 ^ symmetric difference (the union minus the intersection). This
1069 is like an exclusive or, in that the result is the set of code
1070 points that are matched by either, but not both, of the
1073 There is one unary operator:
1077 All the binary operators left associate; C<"&"> is higher precedence
1078 than the others, which all have equal precedence. The unary operator
1079 right associates, and has highest precedence. Thus this follows the
1080 normal Perl precedence rules for logical operators. Use parentheses to
1081 override the default precedence and associativity.
1083 The main restriction is that everything is a metacharacter. Thus,
1084 you cannot refer to single characters by doing something like this:
1086 /(?[ a + b ])/ # Syntax error!
1088 The easiest way to specify an individual typable character is to enclose
1093 (This is the same thing as C<[ab]>.) You could also have said the
1098 (You can, of course, specify single characters by using, C<\x{...}>,
1101 This last example shows the use of this construct to specify an ordinary
1102 bracketed character class without additional set operations. Note the
1103 white space within it. This is allowed because C<E<sol>xx> is
1104 automatically turned on within this construct.
1106 All the other escapes accepted by normal bracketed character classes are
1107 accepted here as well.
1109 Because this construct compiles under
1110 L<C<use re 'strict>|re/'strict' mode>, unrecognized escapes that
1111 generate warnings in normal classes are fatal errors here, as well as
1112 all other warnings from these class elements, as well as some
1113 practices that don't currently warn outside C<re 'strict'>. For example
1116 /(?[ [ \xF ] ])/ # Syntax error!
1118 You have to have two hex digits after a braceless C<\x> (use a leading
1119 zero to make two). These restrictions are to lower the incidence of
1120 typos causing the class to not match what you thought it would.
1122 If a regular bracketed character class contains a C<\p{}> or C<\P{}> and
1123 is matched against a non-Unicode code point, a warning may be
1124 raised, as the result is not Unicode-defined. No such warning will come
1125 when using this extended form.
1127 The final difference between regular bracketed character classes and
1128 these, is that it is not possible to get these to match a
1129 multi-character fold. Thus,
1133 does not match the string C<ss>.
1135 You don't have to enclose POSIX class names inside double brackets,
1136 hence both of the following work:
1138 /(?[ [:word:] - [:lower:] ])/
1139 /(?[ [[:word:]] - [[:lower:]] ])/
1141 Any contained POSIX character classes, including things like C<\w> and C<\D>
1142 respect the C<E<sol>a> (and C<E<sol>aa>) modifiers.
1144 Note that C<< (?[ ]) >> is a regex-compile-time construct. Any attempt
1145 to use something which isn't knowable at the time the containing regular
1146 expression is compiled is a fatal error. In practice, this means
1147 just three limitations:
1153 When compiled within the scope of C<use locale> (or the C<E<sol>l> regex
1154 modifier), this construct assumes that the execution-time locale will be
1155 a UTF-8 one, and the generated pattern always uses Unicode rules. What
1156 gets matched or not thus isn't dependent on the actual runtime locale, so
1157 tainting is not enabled. But a C<locale> category warning is raised
1158 if the runtime locale turns out to not be UTF-8.
1163 L<user-defined property|perlunicode/"User-Defined Character Properties">
1164 used must be already defined by the time the regular expression is
1165 compiled (but note that this construct can be used instead of such
1170 A regular expression that otherwise would compile
1171 using C<E<sol>d> rules, and which uses this construct will instead
1172 use C<E<sol>u>. Thus this construct tells Perl that you don't want
1173 C<E<sol>d> rules for the entire regular expression containing it.
1177 Note that skipping white space applies only to the interior of this
1178 construct. There must not be any space between any of the characters
1179 that form the initial C<(?[>. Nor may there be space between the
1180 closing C<])> characters.
1182 Just as in all regular expressions, the pattern can be built up by
1183 including variables that are interpolated at regex compilation time.
1184 But its best to compile each sub-component.
1186 my $thai_or_lao = qr/(?[ \p{Thai} + \p{Lao} ])/;
1187 my $lower = qr/(?[ \p{Lower} + \p{Digit} ])/;
1189 When these are embedded in another pattern, what they match does not
1190 change, regardless of parenthesization or what modifiers are in effect
1191 in that outer pattern. If you fail to compile the subcomponents, you
1192 can get some nasty surprises. For example:
1194 my $thai_or_lao = '\p{Thai} + \p{Lao}';
1196 qr/(?[ \p{Digit} & $thai_or_lao ])/;
1200 qr/(?[ \p{Digit} & \p{Thai} + \p{Lao} ])/;
1202 But this does not have the effect that someone reading the source code
1203 would likely expect, as the intersection applies just to C<\p{Thai}>,
1204 excluding the Laotian. Its best to compile the subcomponents, but you
1205 could also parenthesize the component pieces:
1207 my $thai_or_lao = '( \p{Thai} + \p{Lao} )';
1209 But any modifiers will still apply to all the components:
1211 my $lower = '\p{Lower} + \p{Digit}';
1212 qr/(?[ \p{Greek} & $lower ])/i;
1214 matches upper case things. So just, compile the subcomponents, as
1217 Due to the way that Perl parses things, your parentheses and brackets
1218 may need to be balanced, even including comments. If you run into any
1219 examples, please submit them to L<https://github.com/Perl/perl5/issues>,
1220 so that we can have a concrete example for this man page.
1222 We may change it so that things that remain legal uses in normal bracketed
1223 character classes might become illegal within this experimental
1224 construct. One proposal, for example, is to forbid adjacent uses of the
1225 same character, as in C<(?[ [aa] ])>. The motivation for such a change
1226 is that this usage is likely a typo, as the second "a" adds nothing.