PERLRECHARCLASS(1perl)
💖 perlrecharclass(1perl) — Perl Programmers Reference Guide 💖
✨ NAME ✨
perlrecharclass — Perl Regular Expression Character Classes 💅
🌈 DESCRIPTION 🌈
Okay bestie, the high-level lore about Perl regexes lives over in perlre. This page right here? It's all about character classes in Perl regular expressions. 💖
A character class is a way of denoting a set of characters so that one character from that set gets matched. Super important, no cap: matching a character class consumes exactly one character in the source string. (The source string is the string the regex is being matched against, bestie. That's the whole vibe.)
Perl regexes have three types of character classes:
- the dot
- backslash sequences
- the form enclosed in square brackets
But keep in mind — the term "character class" is often used to mean just the bracketed form. And honestly? Most Perl docs do exactly that. 🙈
✨ The dot ✨
The dot (or period), ., is probably the most used and certainly the most well-known character class. By default, a dot matches any character except the newline. You can change that default to also match the newline with the single line modifier: for the entire regex using the /s modifier, or locally with (?s) — and even globally within the scope of use re '/s'. (The \N backslash sequence, described below, matches any character except newline without regard to the single line modifier.) 🌟
Here are some examples:
"a" =~ /./ # Match
"." =~ /./ # Match
"" =~ /./ # No match (dot has to match a character)
"\n" =~ /./ # No match (dot does not match a newline)
"\n" =~ /./s # Match (global 'single line' modifier)
"\n" =~ /(?s:.)/ # Match (local 'single line' modifier)
"ab" =~ /^.$/ # No match (dot matches one character)🦋 Backslash sequences 🦋
A backslash sequence is a sequence of characters where the first one is a backslash. Perl gives special meaning to many of these, and some of them are character classes. That means each one matches a single character, as long as that character belongs to the specific set defined by the sequence. 💫
Here's the list of backslash sequences that are character classes — they get discussed in more detail below. (For backslash sequences that aren't character classes, go see perlrebackslash.)
\d— Match a decimal digit character.\D— Match a non-decimal-digit character.\w— Match a "word" character.\W— Match a non-"word" character.\s— Match a whitespace character.\S— Match a non-whitespace character.\h— Match a horizontal whitespace character.\H— Match a character that isn't horizontal whitespace.\v— Match a vertical whitespace character.\V— Match a character that isn't vertical whitespace.\N— Match a character that isn't a newline.\pP,\p{Prop}— Match a character that has the given Unicode property.\PP,\P{Prop}— Match a character that doesn't have the Unicode property.
💀 \N 💀
\N, available starting in v5.12, is like the dot: it matches any character that is not a newline. The difference? \N is not influenced by the single line regular expression modifier (see "The dot" above). 👑
Note that the form \N{...} may mean something completely different. When the {...} is a quantifier, it means to match a non-newline character that many times. For example, \N{3} means match 3 non-newlines; \N{5,} means match 5 or more non-newlines. But if {...} is not a legal quantifier, it's presumed to be a named character. See charnames for those. For example, none of \N{COLON}, \N{4F}, and \N{F4} contain legal quantifiers, so Perl will try to find characters whose names are respectively "COLON", "4F", and "F4". 🌸
🔢 Digits 🔢
\d matches a single character considered to be a decimal digit. If the /a regular expression modifier is in effect, it matches [0-9]. Otherwise, it matches anything that is matched by \p{Digit}, which includes [0-9]. (An unlikely possible exception: under locale matching rules, the current locale might not have [0-9] matched by \d, and/or might match other characters whose code point is less than 256. The only such locale definitions that are legal would be to match [0-9] plus another set of 10 consecutive digit characters; anything else would be in violation of the C language standard, but Perl doesn't currently assume anything in regard to this.) 😭
What this means is that unless the /a modifier is in effect, \d not only matches the digits '0' - '9', but also Arabic, Devanagari, and digits from other languages. This may cause some confusion, and some security issues. 💀
Some digits that \d matches look like some of the [0-9] ones, but have different values. For example, BENGALI DIGIT FOUR (U+09EA) looks very much like an ASCII DIGIT EIGHT (U+0038), and LEPCHA DIGIT SIX (U+1C46) looks very much like an ASCII DIGIT FIVE (U+0035). An application that is expecting only the ASCII digits might be misled, or if the match is \d+, the matched string might contain a mixture of digits from different writing systems that look like they signify a number different than they actually do. num() in Unicode::UCD can be used to safely calculate the value, returning undef if the input string contains such a mixture. Otherwise, for example, a displayed price might be deliberately different than it appears. 😭
What \p{Digit} means (and hence \d except under the /a modifier) is \p{General_Category=Decimal_Number}, or synonymously, \p{General_Category=Digit}. Starting with Unicode version 4.1, this is the same set of characters matched by \p{Numeric_Type=Decimal}. But Unicode also has a different property with a similar name, \p{Numeric_Type=Digit}, which matches a completely different set of characters. These characters are things such as "CIRCLED DIGIT ONE" or subscripts, or are from writing systems that lack all ten digits. 👑
The design intent is for \d to exactly match the set of characters that can safely be used with "normal" big-endian positional decimal syntax, where, for example, 123 means one 'hundred', plus two 'tens', plus three 'ones'. This positional notation does not necessarily apply to characters that match the other type of "digit", \p{Numeric_Type=Digit}, and so \d doesn't match them. ✨
The Tamil digits (U+0BE6 - U+0BEF) can also legally be used in old-style Tamil numbers in which they would appear no more than one in a row, separated by characters that mean "times 10", "times 100", etc. (See <https://www.unicode.org/notes/tn21>.) 🎀
Any character not matched by \d is matched by \D. 💜
👑 Word characters 👑
A \w matches a single alphanumeric character (an alphabetic character, or a decimal digit); or a connecting punctuation character, such as an underscore (_); or a "mark" character (like some sort of accent) that attaches to one of those. It does not match a whole word. To match a whole word, use \w+. This isn't the same thing as matching an English word, but in the ASCII range it is the same as a string of Perl-identifier characters. 🌟
If the /a modifier is in effect ...
\wmatches the 63 characters[a-zA-Z0-9_].
otherwise ...
- For code points above 255 ...
\wmatches the same as\p{Word}matches in this range. That is, it matches Thai letters, Greek letters, etc. This includes connector punctuation (like the underscore) which connect two words together, or diacritics, such as a "COMBINING TILDE" and the modifier letters, which are generally used to add auxiliary markings to letters. 🦋
- For code points below 256 ...
- if locale rules are in effect ...
\wmatches the platform's native underscore character plus whatever the locale considers to be alphanumeric.
- if, instead, Unicode rules are in effect ...
\wmatches exactly what\p{Word}matches.
- otherwise ...
\wmatches[a-zA-Z0-9_].
- if locale rules are in effect ...
Which rules apply are determined as described in "Which character set modifier is in effect?" in perlre. ✨
There are a number of security issues with the full Unicode list of word characters. See <https://unicode.org/reports/tr36>. 💀
Also, for a somewhat finer-grained set of characters that are in programming language identifiers beyond the ASCII range, you may wish to instead use the more customized "Unicode Properties", \p{ID_Start}, \p{ID_Continue}, \p{XID_Start}, and \p{XID_Continue}. See <https://unicode.org/reports/tr31>. 🌈
Any character not matched by \w is matched by \W. 💜
🍓 Whitespace 🍓
\s matches any single character considered whitespace.
If the /a modifier is in effect ...
- In all Perl versions,
\smatches the 5 characters[\t\n\f\r ]; that is, the horizontal tab, the newline, the form feed, the carriage return, and the space. Starting in Perl v5.18, it also matches the vertical tab,\cK. See note "[1]" below for a discussion of this. 😭
otherwise ...
- For code points above 255 ...
\smatches exactly the code points above 255 shown with an "s" column in the table below.
- For code points below 256 ...
- if locale rules are in effect ...
\smatches whatever the locale considers to be whitespace.
- if, instead, Unicode rules are in effect ...
\smatches exactly the characters shown with an "s" column in the table below.
- otherwise ...
\smatches[\t\n\f\r ]and, starting in Perl v5.18, the vertical tab,\cK. (See note "[1]" below for a discussion of this.) Note that this list doesn't include the non-breaking space. 🎀
- if locale rules are in effect ...
Which rules apply are determined as described in "Which character set modifier is in effect?" in perlre. ✨
Any character not matched by \s is matched by \S. 💜
\h matches any character considered horizontal whitespace; this includes the platform's space and tab characters and several others listed in the table below. \H matches any character not considered horizontal whitespace. They use the platform's native character set, and do not consider any locale that may otherwise be in use. 🌸
"\v" matches any character that counts as vertical whitespace — that's the platform's carriage return and line feed characters (newline) plus a bunch of other chars, all of them listed in the table below. And "\V" is the inverse: matches anything that is not considered vertical whitespace. They both use the platform's native character set, and they do not consider any locale that may otherwise be in use.
"\R" matches anything that can be considered a newline under Unicode rules. Heads up bestie: it can match a multi-character sequence. Also it cannot be used inside a bracketed character class — use "\v" (vertical whitespace) instead. It uses the platform's native character set, and doesn't consider any locale that may otherwise be in use either. The details get discussed in perlrebackslash.
Note that unlike "\s" (and "\d" and "\w"), "\h" and "\v" always match the same characters, without regard to other factors, such as the active locale or whether the source string is in UTF-8 format. No vibe check needed, they're consistent like that. ✨
You might think that "\s" is equivalent to [\h\v]. And honestly? True, starting in Perl v5.18. But prior to that, the sole difference was that the vertical tab ("\cK") was not matched by "\s". Iconic little history moment.
The following table is a complete listing of characters matched by "\s", "\h" and "\v" as of Unicode 14.0.
The first column gives the Unicode code point of the character (in hex format), the second column gives the (Unicode) name. The third column indicates by which class(es) the character is matched (assuming no locale is in effect that changes the "\s" matching).
0x0009 CHARACTER TABULATION h s
0x000a LINE FEED (LF) vs
0x000b LINE TABULATION vs [1]
0x000c FORM FEED (FF) vs
0x000d CARRIAGE RETURN (CR) vs
0x0020 SPACE h s
0x0085 NEXT LINE (NEL) vs [2]
0x00a0 NO-BREAK SPACE h s [2]
0x1680 OGHAM SPACE MARK h s
0x2000 EN QUAD h s
0x2001 EM QUAD h s
0x2002 EN SPACE h s
0x2003 EM SPACE h s
0x2004 THREE-PER-EM SPACE h s
0x2005 FOUR-PER-EM SPACE h s
0x2006 SIX-PER-EM SPACE h s
0x2007 FIGURE SPACE h s
0x2008 PUNCTUATION SPACE h s
0x2009 THIN SPACE h s
0x200a HAIR SPACE h s
0x2028 LINE SEPARATOR vs
0x2029 PARAGRAPH SEPARATOR vs
0x202f NARROW NO-BREAK SPACE h s
0x205f MEDIUM MATHEMATICAL SPACE h s
0x3000 IDEOGRAPHIC SPACE h s[1] Prior to Perl v5.18,"\s"did not match the vertical tab."[^\S\cK]"(obscurely) matches what"\s"traditionally did.
[2] NEXT LINE and NO-BREAK SPACE may or may not match "\s" depending on the rules in effect. See the beginning of this section.
👑 Unicode Properties 💅
"\pP" and "\p{Prop}" are character classes that match characters fitting given Unicode properties. One-letter property names can go in the "\pP" form, with the property name following the "\p" — otherwise you need the braces. When you use braces there's a single form, which is just the property name enclosed in the braces, and a compound form that looks like "\p{name=value}", which means match if the property "name" for the character has that particular "value". So for instance, a match for a number can be written as /\pN/ or as /\p{Number}/, or as /\p{Number=True}/.
Lowercase letters get matched by the property Lowercase_Letter, which has the short form Ll. Those need the braces, so they're written as /\p{Ll}/ or /\p{Lowercase_Letter}/, or /\p{General_Category=Lowercase_Letter}/ (the underscores are optional). And /\pLl/ is valid, but it means something totally different — it matches a two character string: a letter (Unicode property "\pL"), followed by a lowercase l. So like, don't get got by that one. 🙈
What a Unicode property matches is never subject to locale rules, and if locale rules are not otherwise in effect, using a Unicode property will force the regular expression into using Unicode rules, if it isn't already.
Note that almost all properties are immune to case-insensitive matching. Meaning adding a /i regular expression modifier does not change what they match. But there are two sets that are affected:
- The first set is
Uppercase_Letter,Lowercase_Letter, andTitlecase_Letter, all of which matchCased_Letterunder/imatching. - The second set is
Uppercase,Lowercase, andTitlecase, all of which matchCasedunder/imatching.
(The difference between these sets is that some things, such as Roman numerals, come in both upper and lower case, so they are "Cased", but aren't considered to be letters, so they aren't "Cased_Letter"s. They're actually "Letter_Number"s.) This set also includes its subsets PosixUpper and PosixLower, both of which under /i match PosixAlpha.
For more details on Unicode properties, see "Unicode Character Properties" in perlunicode; for a complete list of possible properties, see "Properties accessible through \p{} and \P{}" in perluniprops, which notes all forms that have /i differences. It is also possible to define your own properties. This is discussed in "User-Defined Character Properties" in perlunicode.
Unicode properties are defined (surprise!) only on Unicode code points. Starting in v5.20, when matching against "\p" and "\P", Perl treats non-Unicode code points (those above the legal Unicode maximum of 0x10FFFF) as if they were typical unassigned Unicode code points.
Prior to v5.20, Perl raised a warning and made all matches fail on non-Unicode code points. This could be somewhat surprising:
chr(0x110000) =~ \p{ASCII_Hex_Digit=True} # Fails on Perls < v5.20.
chr(0x110000) =~ \p{ASCII_Hex_Digit=False} # Also fails on Perls
# < v5.20Even though these two matches might be thought of as complements, until v5.20 they were so only on Unicode code points.
Starting in perl v5.30, wildcards are allowed in Unicode property values. See "Wildcards in Property Values" in perlunicode.
🍓 Examples 🍓
"a" =~ /\w/ # Match, "a" is a 'word' character.
"7" =~ /\w/ # Match, "7" is a 'word' character as well.
"a" =~ /\d/ # No match, "a" isn't a digit.
"7" =~ /\d/ # Match, "7" is a digit.
" " =~ /\s/ # Match, a space is whitespace.
"a" =~ /\D/ # Match, "a" is a non-digit.
"7" =~ /\D/ # No match, "7" is not a non-digit.
" " =~ /\S/ # No match, a space is not non-whitespace.
" " =~ /\h/ # Match, space is horizontal whitespace.
" " =~ /\v/ # No match, space is not vertical whitespace.
"\r" =~ /\v/ # Match, a return is vertical whitespace.
"a" =~ /\pL/ # Match, "a" is a letter.
"a" =~ /\p{Lu}/ # No match, /\p{Lu}/ matches upper case letters.
"\x{0e0b}" =~ /\p{Thai}/ # Match, \x{0e0b} is the character
# 'THAI CHARACTER SO SO', and that's in
# Thai Unicode class.
"a" =~ /\P{Lao}/ # Match, as "a" is not a Laotian character.It's worth emphasizing that "\d", "\w", etc, match single characters, not complete numbers or words. To match a number (that consists of digits), use "\d+"; to match a word, use "\w+". But be aware of the security considerations in doing so, as mentioned above. 👀
🌸 Bracketed Character Classes 🌸
The third form of character class you can use in Perl regular expressions is the bracketed character class. In its simplest form, it lists the characters that may be matched, surrounded by square brackets, like this: [aeiou]. This matches one of a, e, i, o or u. Like the other character classes, exactly one character is matched.* To match a longer string consisting of characters mentioned in the character class, follow the character class with a quantifier. For instance, [aeiou]+ matches one or more lowercase English vowels. Slay.
Repeating a character in a character class has no effect; it's considered to be in the set only once.
Examples:
"e" =~ /[aeiou]/ # Match, as "e" is listed in the class.
"p" =~ /[aeiou]/ # No match, "p" is not listed in the class.
"ae" =~ /^[aeiou]$/ # No match, a character class only matches
# a single character.
"ae" =~ /^[aeiou]+$/ # Match, due to the quantifier.💀 * There are two exceptions to a bracketed character class matching a single character only. Each requires special handling by Perl to make things work:
- When the class is to match caselessly under
/imatching rules, and a character that is explicitly mentioned inside the class matches a multiple-character sequence caselessly under Unicode rules, the class will also match that sequence. For example, Unicode says that the letterLATIN SMALL LETTER SHARP Sshould match the sequencessunder/irules. Thus,
'ss' =~ /\A\N{LATIN SMALL LETTER SHARP S}\z/i # Matches
'ss' =~ /\A[aeioust\N{LATIN SMALL LETTER SHARP S}]\z/i # MatchesFor this to happen, the class must not be inverted (see "Negation") and the character must be explicitly specified, and not be part of a multi-character range (not even as one of its endpoints). ("Character Ranges" will be explained shortly.) Therefore,
'ss' =~ /\A[\0-\x{ff}]\z/ui # Doesn't match
'ss' =~ /\A[\0-\N{LATIN SMALL LETTER SHARP S}]\z/ui # No match
'ss' =~ /\A[\xDF-\xDF]\z/ui # Matches on ASCII platforms, since
# \xDF is LATIN SMALL LETTER SHARP S,
# and the range is just a single
# elementNote that it isn't a good idea to specify these types of ranges anyway.
- Some names known to
"\N{...}"refer to a sequence of multiple characters, instead of the usual single character. When one of these is included in the class, the entire sequence is matched. For example,
"\N{TAMIL LETTER KA}\N{TAMIL VOWEL SIGN AU}"
=~ / ^ [\N{TAMIL SYLLABLE KAU}] $ /x;...matches, bestie — because \N{TAMIL SYLLABLE KAU} is a named sequence that literally consists of the two characters you just matched against. 🫶
And just like the other spot where a bracketed class can match multiple characters, and for basically the same reasons, the class must not be inverted, and the named sequence may not appear in a range — not even a range where it's both endpoints. If you go and do that anyway: it's a fatal error if the character class is inside the scope of use re 'strict', or inside an extended (?[...]) class. Otherwise only the first code point gets used, and you get a regexp-type warning raised for your trouble. 💀
Special Characters Inside a Bracketed Character Class 🎀
Most characters that are meta characters in regular expressions — yk, the ones that carry a special meaning like ., *, or ( — lose their special meaning and can be used inside a character class without needing to escape them. So [()] matches either an opening parenthesis or a closing parenthesis, and those parens inside the character class don't group or capture anything. But be aware, babe: unless the pattern is evaluated in single-quotish context, variable interpolation happens before the bracketed class is parsed:
$, = "\t| ";
$x =~ m'[$,]'; # single-quotish: matches '$' or ','
$x =~ q{[$,]}; # same
$x =~ m/[$,]/; # double-quotish: Because we made an
# assignment to $, above, this now
# matches "\t", "|", or " "The characters that may carry a special meaning inside a character class are: \, ^, -, [ and ], and we get into all of them below. They can be escaped with a backslash, although sometimes that's not even needed, in which case you can just omit the backslash. 💅
The sequence \b is special inside a bracketed character class. Outside the character class, \b is an assertion indicating a point that doesn't have either two word characters or two non-word characters on either side. Inside a bracketed character class? \b matches a backspace character. iconic, honestly.
The sequences \a, \c, \e, \f, \n, \N{NAME}, \N{U+hex char}, \r, \t, and \x are also special, and they have the same meanings inside a bracketed character class as they do outside one.
Also: a backslash followed by two or three octal digits is considered an octal number. ✨
A [ is not special inside a character class, unless it's the start of a POSIX character class (peep "POSIX Character Classes" below). Normally it doesn't need escaping.
A ] is normally either the end of a POSIX character class (see "POSIX Character Classes" below), or it signals the end of the bracketed character class. So if you want a ] in your set of characters, you generally have to escape it.
HOWEVER — if that ] is the first character of a bracketed character class (or the second, if the first character is a caret), then it does not denote the end of the class (you can't have an empty class, bestie) and it's considered part of the set of characters that can be matched without escaping. 🦋
Examples:
"+" =~ /[+?*]/ # Match, "+" in a character class is not special.
"\cH" =~ /[\b]/ # Match, \b inside in a character class
# is equivalent to a backspace.
"]" =~ /[][]/ # Match, as the character class contains
# both [ and ].
"[]" =~ /[[]]/ # Match, the pattern contains a character class
# containing just [, and the character class is
# followed by a ].Bracketed Character Classes and the /xx pattern modifier 🌸
Normally SPACE and TAB have no special meaning inside a bracketed character class; they just get added to the list of characters matched by the class. But if the /xx pattern modifier is in effect, they're generally ignored and you can add them in to improve readability. They can't be added in the middle of a single construct though:
/ [ \x{10 FFFF} ] /xx # WRONG!The SPACE in the middle of the hex constant is illegal. 🙈
To specify a literal SPACE character, you can escape it with a backslash, like:
/[ a e i o u \ ]/xxThat matches the English vowels plus the SPACE character. 💖
For clarity, you should already have been using \t to specify a literal tab, and \t is unaffected by /xx.
Character Ranges 🌈
It is not uncommon to want to match a range of characters. Luckily, instead of listing every single character in the range, you may use the hyphen (-). If inside a bracketed character class you have two characters separated by a hyphen, it's treated as if all the characters between the two were in the class. So [0-9] matches any ASCII digit, and [a-m] matches any lowercase letter from the first half of the ASCII alphabet. slay. 👑
Note that the two characters on either side of the hyphen are not necessarily both letters or both digits. Any character is possible, although not advisable. ['-?] contains a range of characters, but most people will not know which characters that means. And furthermore? Such ranges may lead to portability problems if the code has to run on a platform that uses a different character set, such as EBCDIC. 😭
If a hyphen in a character class can't syntactically be part of a range — for instance because it's the first or the last character of the character class, or if it immediately follows a range — then the hyphen isn't special, and so it's considered a character to be matched literally. If you want a hyphen in your set of characters to be matched and its position in the class is such that it could be considered part of a range, you must escape that hyphen with a backslash. periodt.
Examples:
[a-z] # Matches a character that is a lower case ASCII letter.
[a-fz] # Matches any letter between 'a' and 'f' (inclusive) or
# the letter 'z'.
[-z] # Matches either a hyphen ('-') or the letter 'z'.
[a-f-m] # Matches any letter between 'a' and 'f' (inclusive), the
# hyphen ('-'), or the letter 'm'.
['-?] # Matches any of the characters '()*+,-./0123456789:;<=>?
# (But not on an EBCDIC platform).
[\N{APOSTROPHE}-\N{QUESTION MARK}]
# Matches any of the characters '()*+,-./0123456789:;<=>?
# even on an EBCDIC platform.
[\N{U+27}-\N{U+3F}] # Same. (U+27 is "'", and U+3F is "?")As those final two examples show, you can achieve portability to non-ASCII platforms by using the \N{...} form for the range endpoints. Those indicate that the specified range is to be interpreted using Unicode values, so [\N{U+27}-\N{U+3F}] means to match \N{U+27}, \N{U+28}, \N{U+29}, ..., \N{U+3D}, \N{U+3E}, and \N{U+3F}, whatever the native code point versions for those are. These are called "Unicode" ranges. If either end is of the \N{...} form, the range is considered Unicode. A regexp warning is raised under use re 'strict' if the other endpoint is specified non-portably:
[\N{U+00}-\x09] # Warning under re 'strict'; \x09 is non-portable
[\N{U+00}-\t] # No warning;Both of the above match the characters \N{U+00} \N{U+01}, ... \N{U+08}, \N{U+09}, but the \x09 looks like it could be a mistake, so the warning is raised (under re 'strict') for it. 💀
Perl also guarantees that the ranges A-Z, a-z, 0-9, and any subranges of these, match what an English-only speaker would expect them to match on any platform. That is, [A-Z] matches the 26 ASCII uppercase letters; [a-z] matches the 26 lowercase letters; and [0-9] matches the 10 digits. Subranges, like [h-k], match correspondingly — in this case just the four letters h, i, j, and k. That's the natural behavior on ASCII platforms, where the code points (ordinal values) for h through k are consecutive integers (0x68 through 0x6B). But special handling to achieve this may be needed on platforms with a non-ASCII native character set. For example, on EBCDIC platforms, the code point for h is 0x88, i is 0x89, j is 0x91, and k is 0x92. Perl specially treats [h-k] to exclude the seven code points in the gap: 0x8A through 0x90. This special handling is only invoked when the range is a subrange of one of the ASCII uppercase, lowercase, and digit ranges, AND each end of the range is expressed either as a literal, like A, or as a named character (\N{...}, including the \N{U+...} form). ikyk. 🧚
EBCDIC Examples:
[i-j] # Matches either "i" or "j"
[i-\N{LATIN SMALL LETTER J}] # Same
[i-\N{U+6A}] # Same
[\N{U+69}-\N{U+6A}] # Same
[\x{89}-\x{91}] # Matches 0x89 ("i"), 0x8A .. 0x90, 0x91 ("j")
[i-\x{91}] # Same
[\x{89}-j] # Same
[i-J] # Matches, 0x89 ("i") .. 0xC1 ("J"); special
# handling doesn't apply because range is mixed
# caseNegation 💅
It is also possible to instead list the characters you do not want to match. You can do that by using a caret (^) as the first character in the character class. So [^a-z] matches any character that is not a lowercase ASCII letter, which therefore includes more than a million Unicode code points. no cap. The class is said to be "negated" or "inverted". ✨
This syntax makes the caret a special character inside a bracketed character class, but only if it is the first character of the class. So if you want the caret as one of the characters to match, either escape the caret or else just don't list it first. 🎀
In inverted bracketed character classes, Perl ignores the Unicode rules that normally say that named sequence, and certain characters, should match a sequence of multiple characters under caseless /i matching. Following those rules could lead to highly confusing situations:
"ss" =~ /^[^\xDF]+$/ui; # Matches!This should match any sequences of characters that aren't \xDF nor what \xDF matches under /i. And s isn't \xDF... but Unicode says that ss is what \xDF matches under /i. So which one wins? Do you fail the match because the string has ss, or accept it because it has an s followed by another s? Perl has chosen the latter. (See note in "Bracketed Character Classes" above.) 😭
Examples:
"e" =~ /[^aeiou]/ # No match, the 'e' is listed.
"x" =~ /[^aeiou]/ # Match, as 'x' isn't a lowercase vowel.
"^" =~ /[^^]/ # No match, matches anything that isn't a caret.
"^" =~ /[x^]/ # Match, caret is not special here.Backslash Sequences 🔥
okay so continuing, bestie 💖
You can put any backslash sequence character class (with the exception of \N and \R) inside a bracketed character class, and it'll act just as if you'd put every single character matched by that backslash sequence inside the character class. For instance, [a-f\d] matches any decimal digit, or any of the lowercase letters between 'a' and 'f' inclusive. slay. ✨
\N inside a bracketed character class must be of the forms \N{name} or \N{U+hex char}, and NOT the form that matches non-newlines — for the exact same reason that a dot . inside a bracketed character class loses its special meaning: it matches nearly anything, which generally isn't what you want to happen. 🙈
Examples:
/[\p{Thai}\d]/ # Matches a character that is either a Thai
# character, or a digit.
/[^\p{Arabic}()]/ # Matches a character that is neither an Arabic
# character, nor a parenthesis.Backslash sequence character classes cannot form one of the endpoints of a range. So you literally can't say:
/[\p{Thai}-\d]/ # Wrong!✨ POSIX Character Classes ✨
POSIX character classes have the form [:class:], where class is the name, and [: and :] are the delimiters. They only ever appear inside bracketed character classes, and they're a convenient and descriptive way of listing a group of characters. 🎀
Be careful about the syntax, fr fr:
# Correct:
$string =~ /[[:alpha:]]/
# Incorrect (will warn):
$string =~ /[:alpha:]/That latter pattern would be a character class consisting of a colon, and the letters a, l, p and h. not what you meant at all 😭
POSIX character classes can be part of a larger bracketed character class. For example,
[01[:alpha:]%]is valid and matches '0', '1', any alphabetic character, and the percent sign. 💅
Perl recognizes the following POSIX character classes:
alpha— Any alphabetical character (e.g.,[A-Za-z]).alnum— Any alphanumeric character (e.g.,[A-Za-z0-9]).ascii— Any character in the ASCII character set.blank— Any horizontal whitespace character (e.g. space or horizontal tab (\t)).cntrl— Any control character. See Note [2] below.digit— Any decimal digit (e.g.,[0-9]), equivalent to\d.graph— Any printable character, excluding a space. See Note [3] below.lower— Any lowercase character (e.g.,[a-z]).print— Any printable character, including a space. See Note [4] below.punct— Any graphical character excluding "word" characters. Note [5].space— Any whitespace character.\sincluding the vertical tab (\cK).upper— Any uppercase character (e.g.,[A-Z]).word— A Perl extension (e.g.,[A-Za-z0-9_]), equivalent to\w.xdigit— Any hexadecimal digit (e.g.,[0-9a-fA-F]). Note [7].
Like the Unicode properties, most of the POSIX properties match the same regardless of whether case-insensitive (/i) matching is in effect or not. The two exceptions are [:upper:] and [:lower:]. Under /i, they each match the union of [:upper:] and [:lower:]. the more you know 🌈
Most POSIX character classes have two Unicode-style \p property counterparts. (They are not official Unicode properties, but Perl extensions derived from official Unicode properties.) The table below shows the relation between POSIX character classes and these counterparts.
One counterpart, in the column labelled "ASCII-range Unicode" in the table, matches only characters in the ASCII character set.
The other counterpart, in the column labelled "Full-range Unicode", matches any appropriate characters in the full Unicode character set. For example, \p{Alpha} matches not just the ASCII alphabetic characters, but any character in the entire Unicode character set considered alphabetic. An entry in the column labelled "backslash sequence" is a (short) equivalent.
[[:...:]] ASCII-range Full-range backslash Note
Unicode Unicode sequence
-----------------------------------------------------
alpha \p{PosixAlpha} \p{XPosixAlpha}
alnum \p{PosixAlnum} \p{XPosixAlnum}
ascii \p{ASCII}
blank \p{PosixBlank} \p{XPosixBlank} \h [1]
or \p{HorizSpace} [1]
cntrl \p{PosixCntrl} \p{XPosixCntrl} [2]
digit \p{PosixDigit} \p{XPosixDigit} \d
graph \p{PosixGraph} \p{XPosixGraph} [3]
lower \p{PosixLower} \p{XPosixLower}
print \p{PosixPrint} \p{XPosixPrint} [4]
punct \p{PosixPunct} \p{XPosixPunct} [5]
\p{PerlSpace} \p{XPerlSpace} \s [6]
space \p{PosixSpace} \p{XPosixSpace} [6]
upper \p{PosixUpper} \p{XPosixUpper}
word \p{PosixWord} \p{XPosixWord} \w
xdigit \p{PosixXDigit} \p{XPosixXDigit} [7][1] \p{Blank} and \p{HorizSpace} are synonyms.
[2] Control characters don't produce output as such, but instead usually control the terminal somehow: for example, newline and backspace are control characters. On ASCII platforms, in the ASCII range, characters whose code points are between 0 and 31 inclusive, plus 127 (DEL) are control characters; on EBCDIC platforms, their counterparts are control characters.
[3] Any character that is graphical, that is, visible. This class consists of all alphanumeric characters and all punctuation characters.
[4] All printable characters, which is the set of all graphical characters plus those whitespace characters which are not also controls.
[5] \p{PosixPunct} and [[:punct:]] in the ASCII range match all non-controls, non-alphanumeric, non-space characters: [-!"#$%&'()*+,./:;<=>?@[\\\]^_`{|}~] (although if a locale is in effect, it could alter the behavior of [[:punct:]]).
The similarly named property, \p{Punct}, matches a somewhat different set in the ASCII range, namely [-!"#%&'()*,./:;?@[\\\]_{}]. That is, it is missing the nine characters [$+<=>^`|~]. This is because Unicode splits what POSIX considers to be punctuation into two categories, Punctuation and Symbols.
\p{XPosixPunct} and (under Unicode rules) [[:punct:]], match what \p{PosixPunct} matches in the ASCII range, plus what \p{Punct} matches. This is different than strictly matching according to \p{Punct}. Another way to say it is that if Unicode rules are in effect, [[:punct:]] matches all characters that Unicode considers punctuation, plus all ASCII-range characters that Unicode considers symbols.
[6] \p{XPerlSpace} and \p{Space} match identically starting with Perl v5.18. In earlier versions, these differ only in that in non-locale matching, \p{XPerlSpace} did not match the vertical tab, \cK. Same for the two ASCII-only range forms.
[7] Unlike [[:digit:]] which matches digits in many writing systems, such as Thai and Devanagari, there are currently only two sets of hexadecimal digits, and it is unlikely that more will be added. This is because you not only need the ten digits, but also the six [A-F] (and [a-f]) to correspond. That means only the Latin script is suitable for these, and Unicode has only two sets of these, the familiar ASCII set, and the fullwidth forms starting at U+FF10 (FULLWIDTH DIGIT ZERO).
There are various other synonyms that can be used besides the names listed in the table. For example, \p{XPosixAlpha} can be written as \p{Alpha}. All are listed in "Properties accessible through \p{} and \P{}" in perluniprops. 🦋
Both the \p counterparts always assume Unicode rules are in effect. On ASCII platforms, this means they assume that the code points from 128 to 255 are Latin-1, and that means that using them under locale rules is unwise unless the locale is guaranteed to be Latin-1 or UTF-8. In contrast, the POSIX character classes are useful under locale rules. They are affected by the actual rules in effect, as follows:
- If the
/amodifier, is in effect ...- Each of the POSIX classes matches exactly the same as their ASCII-range counterparts.
- otherwise ...
- For code points above 255 ...
- The POSIX class matches the same as its Full-range counterpart.
- For code points below 256 ...
- if locale rules are in effect ...
- The POSIX class matches according to the locale, except:
word— also includes the platform's native underscore character, no matter what the locale is.ascii— on platforms that don't have the POSIXasciiextension, this matches just the platform's native ASCII-range characters.blank— on platforms that don't have the POSIXblankextension, this matches just the platform's native tab and space characters.
- if, instead, Unicode rules are in effect ...
- The POSIX class matches the same as the Full-range counterpart.
- otherwise ...
- The POSIX class matches the same as the ASCII range counterpart.
- if locale rules are in effect ...
- For code points above 255 ...
Which rules apply are determined as described in "Which character set modifier is in effect?" in perlre.
💫 Negation of POSIX character classes 💫
A Perl extension to the POSIX character class is the ability to negate it. This is done by prefixing the class name with a caret (^). Some examples:
POSIX ASCII-range Full-range backslash
Unicode Unicode sequence
-----------------------------------------------------
[[:^digit:]] \P{PosixDigit} \P{XPosixDigit} \D
[[:^space:]] \P{PosixSpace} \P{XPosixSpace}
\P{PerlSpace} \P{XPerlSpace} \S
[[:^word:]] \P{PerlWord} \P{XPosixWord} \WThe backslash sequence can mean either ASCII- or Full-range Unicode, depending on various factors as described in "Which character set modifier is in effect?" in perlre. 👑
🎀 [= =] and [. .] 🎀
Perl recognizes the POSIX character classes [=class=] and [.class.], but does not (yet?) support them. Any attempt to use either construct raises an exception. 💀
🌸 Examples 🌸
...and lowkey these next ones are the chef's kiss combos where you just throw POSIX classes straight into a bracketed class and let them vibe together 💖
/[[:digit:]]/ # Matches a character that is a digit.
/[01[:lower:]]/ # Matches a character that is either a
# lowercase letter, or '0' or '1'.
/[[:digit:][:^xdigit:]]/ # Matches a character that can be anything
# except the letters 'a' to 'f' and 'A' to
# 'F'. This is because the main character
# class is composed of two POSIX character
# classes that are ORed together, one that
# matches any digit, and the other that
# matches anything that isn't a hex digit.
# The OR adds the digits, leaving only the
# letters 'a' to 'f' and 'A' to 'F' excluded.🌈 Extended Bracketed Character Classes 🌈
(they also call it "regex_sets", iykyk)
Okay bestie, this is the fancy bracketed character class. It's giving readable, it's giving less error-prone, and most iconic of all — it does set operations, like intersection. Behold:
/(?[ \p{Thai} & \p{Digit} ])/That matches every digit character that lives in the Thai script. 🎀
This feature showed up in Perl 5.18 as experimental, and got officially accepted in 5.36. Character development, honestly 👑
The rules from use re 'strict' apply to this construct too. No chaos allowed.
We can stack the example up even more:
/(?[ ( \p{Thai} + \p{Lao} ) & \p{Digit} ])/which matches digits in either the Thai or Laotian scripts. Look at that white space though — notice it? This construct always has the /xx modifier turned on inside it, so breather space is totally allowed. 💅
Here are the binary operators on offer:
&— intersection+— union|— another name for+, hence means union-— subtraction (the result matches the set consisting of those code points matched by the first operand, excluding any that are also matched by the second operand)^— symmetric difference (the union minus the intersection). This is like an exclusive or, in that the result is the set of code points that are matched by either, but not both, of the operands.
And exactly one unary operator:
!— complement
All the binary operators left associate, and & is higher precedence than the others, which all have equal precedence. The unary operator right associates and has the highest precedence of everyone. So basically it follows the normal Perl precedence rules for logical operators — if you wanna override the default precedence and associativity, use parentheses. Periodt.
The main restriction? Everything is a metacharacter. So no, you cannot refer to single characters like this:
/(?[ a + b ])/ # Syntax error!Nope. Syntax error, sorry babe 😭
The easiest way to specify an individual typable character is to wrap it in brackets:
/(?[ [a] + [b] ])/(That's the same thing as [ab].) You could also have said the equivalent:
/(?[[ a b ]])/(And you can, of course, specify single characters by using \x{...}, \N{...}, etc.)
That last example shows you using this construct to specify an ordinary bracketed character class without any extra set operations. Note the white space within it — that's allowed because /xx is automatically turned on within this construct. 🦋
All the other escapes that normal bracketed character classes accept are accepted here as well.
Because this construct compiles under use re 'strict', unrecognized escapes that would just generate warnings in normal classes are fatal errors here. Same for all other warnings from these class elements, plus some practices that don't currently warn outside re 'strict'. For example you cannot say:
/(?[ [ \xF ] ])/ # Syntax error!You have to have two hex digits after a braceless \x (use a leading zero to make two). These restrictions exist so typos don't silently make your class not match what you thought it would. Protective queen behavior, honestly 🫶
If a regular bracketed character class contains a \p{} or \P{} and gets matched against a non-Unicode code point, a warning may be raised, because the result isn't Unicode-defined. No such warning will come when you're using this extended form. ✨
The final difference between regular bracketed character classes and these: it is not possible to get these to match a multi-character fold. So:
/(?[ [\xDF] ])/iudoes not match the string "ss". Wild, right? 💀
You don't have to enclose POSIX class names inside double brackets, so both of these work:
/(?[ [:word:] - [:lower:] ])/
/(?[ [[:word:]] - [[:lower:]] ])/Any contained POSIX character classes — including things like \w and \D — respect the /a (and /aa) modifiers. 👑
Note that (?[ ]) is a regex-compile-time construct. Any attempt to use something which isn't knowable at the time the containing regular expression is compiled is a fatal error. In practice, that means just three limitations:
- When compiled within the scope of
use locale(or the/lregex modifier), this construct assumes that the execution-time locale will be a UTF-8 one, and the generated pattern always uses Unicode rules. What gets matched or not thus isn't dependent on the actual runtime locale, so tainting is not enabled. But alocalecategory warning is raised if the runtime locale turns out to not be UTF-8. - Any user-defined property used must be already defined by the time the regular expression is compiled (but note that this construct can be used instead of such properties).
- A regular expression that otherwise would compile using
/drules and which uses this construct will instead use/u. Thus this construct tells Perl that you don't want/drules for the entire regular expression containing it.
⚠️ Note that skipping white space applies only to the interior of this construct. There must not be any space between any of the characters that form the initial(?[, nor may there be space between the closing])characters. No sneaky spaces, bestie.
Just as in all regular expressions, the pattern can be built up by including variables that are interpolated at regex compilation time. But currently each such sub-component should be an already-compiled extended bracketed character class.
my $thai_or_lao = qr/(?[ \p{Thai} + \p{Lao} ])/;
...
qr/(?[ \p{Digit} & $thai_or_lao ])/;If you interpolate something else, the pattern may still compile (or it may die), but if it compiles, it very well may not behave as you would expect:
my $thai_or_lao = '\p{Thai} + \p{Lao}';
qr/(?[ \p{Digit} & $thai_or_lao ])/;compiles to
qr/(?[ \p{Digit} & \p{Thai} + \p{Lao} ])/;And that does not have the effect that someone reading the source code would likely expect, because the intersection applies just to \p{Thai}, excluding the Laotian. 😭 Set operations said surprise.
Due to the way that Perl parses things, your parentheses and brackets may need to be balanced, even including comments. If you run into any examples, please submit them to https://github.com/Perl/perl5/issues, so that we can have a concrete example for this man page. Do it for the girls 🧚
and that's the whole page, bestie!! you made it all the way to the end, main character energy fr fr 👑💖 this one's from perl v5.44.0, dated 2026-10-17, and the page is PERLRECHARCLASS(1perl) — go forth and match some characters, you're absolutely slaying 🌸🦋✨
📦 where this page comes from
- arch rolling: perl 5.44.0-1 · Artistic-1.0-Perl AND GPL-1.0-or-later
- 💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash on : a language model's rewrite of the original, under its terms