perlrecharclass
(1)
Name
perlrecharclass - Perl Regular Expression Character Classes
Synopsis
Please see following description for synopsis
Description
Perl Programmers Reference Guide PERLRECHARCLASS(1)
NAME
perlrecharclass - Perl Regular Expression Character Classes
DESCRIPTION
The top level documentation about Perl regular expressions
is found in perlre.
This manual page discusses the syntax and use of character
classes in Perl regular expressions.
A character class is a way of denoting a set of characters
in such a way that one character of the set is matched.
It's important to remember that: matching a character class
consumes exactly one character in the source string. (The
source string is the string the regular expression is
matched against.)
There are three types of character classes in Perl regular
expressions: the dot, backslash sequences, and the form
enclosed in square brackets. Keep in mind, though, that
often the term "character class" is used to mean just the
bracketed form. Certainly, most Perl documentation does
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 for the newline. The
default can be changed to add matching the newline by using
the single line modifier: either for the entire regular
expression with the "/s" modifier, or locally with "(?s)".
(The experimental "\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, the first
one of which is a backslash. Perl ascribes special meaning
to many such sequences, and some of these are character
classes. That is, they match a single character each,
provided that the character belongs to the specific set of
characters defined by the sequence.
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Here's a list of the backslash sequences that are character
classes. They are discussed in more detail below. (For the
backslash sequences that aren't character classes, 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. Experimental.
\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
Digits
"\d" matches a single character that is considered to be a
decimal digit. What is considered a decimal digit depends
on the internal encoding of the source string and the locale
that is in effect. If the source string is in UTF-8 format,
"\d" not only matches the digits '0' - '9', but also Arabic,
Devanagari and digits from other languages. Otherwise, if
there is a locale in effect, it will match whatever
characters the locale considers decimal digits. Without a
locale, "\d" matches just the digits '0' to '9'. See
"Locale, EBCDIC, Unicode and UTF-8".
Unicode digits may cause some confusion, and some security
issues. In UTF-8 strings, "\d" matches the same characters
matched by "\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 subscripts.
The design intent is for "\d" to match all the digits (and
no other characters) that can be used with "normal" big-
endian positional decimal syntax, whereby a sequence of such
digits {N0, N1, N2, ...Nn} has the numeric value (...(N0 *
10 + N1) * 10 + N2) * 10 ... + Nn). In Unicode 5.2, 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
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10", "times 100", etc. (See
<http://www.unicode.org/notes/tn21>.)
Some of the non-European digits that "\d" matches look like
European ones, but have different values. For example,
BENGALI DIGIT FOUR (U+09A) looks very much like an ASCII
DIGIT EIGHT (U+0038).
It may be useful for security purposes for an application to
require that all digits in a row be from the same script.
See "charscript()" in Unicode::UCD.
Any character that isn't matched by "\d" will be matched by
"\D".
Word characters
A "\w" matches a single alphanumeric character (an
alphabetic character, or a decimal digit) or an underscore
("_"), not a whole word. To match a whole word, use "\w+".
This isn't the same thing as matching an English word, but
is the same as a string of Perl-identifier characters. What
is considered a word character depends on the internal
encoding of the string and the locale or EBCDIC code page
that is in effect. If it's in UTF-8 format, "\w" matches
those characters that are considered word characters in the
Unicode database. That is, it not only matches ASCII
letters, but also Thai letters, Greek letters, etc. If the
source string isn't in UTF-8 format, "\w" matches those
characters that are considered word characters by the
current locale or EBCDIC code page. Without a locale or
EBCDIC code page, "\w" matches the ASCII letters, digits and
the underscore. See "Locale, EBCDIC, Unicode and UTF-8".
There are a number of security issues with the full Unicode
list of word characters. See
<http://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, "ID_Start", ID_Continue", "XID_Start",
and "XID_Continue". See <http://unicode.org/reports/tr31>.
Any character that isn't matched by "\w" will be matched by
"\W".
Whitespace
"\s" matches any single character that is considered
whitespace. The exact set of characters matched by "\s"
depends on whether the source string is in UTF-8 format and
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the locale or EBCDIC code page that is in effect. If it's in
UTF-8 format, "\s" matches what is considered whitespace in
the Unicode database; the complete list is in the table
below. Otherwise, if there is a locale or EBCDIC code page
in effect, "\s" matches whatever is considered whitespace by
the current locale or EBCDIC code page. Without a locale or
EBCDIC code page, "\s" matches the horizontal tab ("\t"),
the newline ("\n"), the form feed ("\f"), the carriage
return ("\r"), and the space. (Note that it doesn't match
the vertical tab, "\cK".) Perhaps the most notable possible
surprise is that "\s" matches a non-breaking space only if
the non-breaking space is in a UTF-8 encoded string or the
locale or EBCDIC code page that is in effect has that
character. See "Locale, EBCDIC, Unicode and UTF-8".
Any character that isn't matched by "\s" will be matched by
"\S".
"\h" will match any character that is considered horizontal
whitespace; this includes the space and the tab characters
and a number other characters, all of which are listed in
the table below. "\H" will match any character that is not
considered horizontal whitespace.
"\v" will match any character that is considered vertical
whitespace; this includes the carriage return and line feed
characters (newline) plus several other characters, all
listed in the table below. "\V" will match any character
that is not considered vertical whitespace.
"\R" matches anything that can be considered a newline under
Unicode rules. It's not a character class, as it can match a
multi-character sequence. Therefore, it cannot be used
inside a bracketed character class; use "\v" instead
(vertical whitespace). Details are discussed in
perlrebackslash.
Note that unlike "\s", "\d" and "\w", "\h" and "\v" always
match the same characters, regardless whether the source
string is in UTF-8 format or not. The set of characters they
match is also not influenced by locale nor EBCDIC code page.
One might think that "\s" is equivalent to "[\h\v]". This is
not true. The vertical tab ("\x0b") is not matched by "\s",
it is however considered vertical whitespace. Furthermore,
if the source string is not in UTF-8 format, and any locale
or EBCDIC code page that is in effect doesn't include them,
the next line (ASCII-platform "\x85") and the no-break space
(ASCII-platform "\xA0") characters are not matched by "\s",
but are by "\v" and "\h" respectively. If the source string
is in UTF-8 format, both the next line and the no-break
space are matched by "\s".
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The following table is a complete listing of characters
matched by "\s", "\h" and "\v" as of Unicode 5.2.
The first column gives the 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 or EBCDIC code page is in effect
that changes the "\s" matching).
0x00009 CHARACTER TABULATION h s
0x0000a LINE FEED (LF) vs
0x0000b LINE TABULATION v
0x0000c FORM FEED (FF) vs
0x0000d CARRIAGE RETURN (CR) vs
0x00020 SPACE h s
0x00085 NEXT LINE (NEL) vs [1]
0x000a0 NO-BREAK SPACE h s [1]
0x01680 OGHAM SPACE MARK h s
0x0180e MONGOLIAN VOWEL SEPARATOR h s
0x02000 EN QUAD h s
0x02001 EM QUAD h s
0x02002 EN SPACE h s
0x02003 EM SPACE h s
0x02004 THREE-PER-EM SPACE h s
0x02005 FOUR-PER-EM SPACE h s
0x02006 SIX-PER-EM SPACE h s
0x02007 FIGURE SPACE h s
0x02008 PUNCTUATION SPACE h s
0x02009 THIN SPACE h s
0x0200a HAIR SPACE h s
0x02028 LINE SEPARATOR vs
0x02029 PARAGRAPH SEPARATOR vs
0x0202f NARROW NO-BREAK SPACE h s
0x0205f MEDIUM MATHEMATICAL SPACE h s
0x03000 IDEOGRAPHIC SPACE h s
[1] NEXT LINE and NO-BREAK SPACE only match "\s" if the
source string is in UTF-8 format, or the locale or
EBCDIC code page that is in effect includes them.
It is worth noting that "\d", "\w", etc, match single
characters, not complete numbers or words. To match a number
(that consists of integers), use "\d+"; to match a word, use
"\w+".
\N
"\N" is new in 5.12, and is experimental. It, like the dot,
will match any character that is not a newline. The
difference is that "\N" is not influenced by the single line
regular expression modifier (see "The dot" above). Note
that the form "\N{...}" may mean something completely
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different. When the "{...}" is a quantifier, it means to
match a non-newline character that many times. For example,
"\N{3}" means to match 3 non-newlines; "\N{5,}" means to
match 5 or more non-newlines. But if "{...}" is not a legal
quantifier, it is 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".
Unicode Properties
"\pP" and "\p{Prop}" are character classes to match
characters that fit given Unicode properties. One letter
property names can be used in the "\pP" form, with the
property name following the "\p", otherwise, braces are
required. When using braces, there is a single form, which
is just the property name enclosed in the braces, and a
compound form which looks like "\p{name=value}", which means
to match if the property "name" for the character has the
particular "value". For instance, a match for a number can
be written as "/\pN/" or as "/\p{Number}/", or as
"/\p{Number=True}/". Lowercase letters are matched by the
property Lowercase_Letter which has as short form Ll. They
need the braces, so are written as "/\p{Ll}/" or
"/\p{Lowercase_Letter}/", or
"/\p{General_Category=Lowercase_Letter}/" (the underscores
are optional). "/\pLl/" is valid, but means something
different. It matches a two character string: a letter
(Unicode property "\pL"), followed by a lowercase "l".
For more details, see "Unicode Character Properties" in
perlunicode; for a complete list of possible properties, see
"Properties accessible through \p{} and \P{}" in
perluniprops. It is also possible to define your own
properties. This is discussed in "User-Defined Character
Properties" 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.
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"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.
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 will
be 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 a string of one or more lowercase English vowels.
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.
Special Characters Inside a Bracketed Character Class
Most characters that are meta characters in regular
expressions (that is, characters that carry a special
meaning like ".", "*", or "(") lose their special meaning
and can be used inside a character class without the need to
escape them. For instance, "[()]" matches either an opening
parenthesis, or a closing parenthesis, and the parens inside
the character class don't group or capture.
Characters that may carry a special meaning inside a
character class are: "\", "^", "-", "[" and "]", and are
discussed below. They can be escaped with a backslash,
although this is sometimes not needed, in which case the
backslash may be omitted.
The sequence "\b" is special inside a bracketed character
class. While outside the character class, "\b" is an
assertion indicating a point that does not have either two
word characters or two non-word characters on either side,
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inside a bracketed character class, "\b" matches a backspace
character.
The sequences "\a", "\c", "\e", "\f", "\n", "\N{NAME}",
"\N{U+wide hex char}", "\r", "\t", and "\x" are also special
and have the same meanings as they do outside a bracketed
character class.
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 (see "POSIX Character
Classes" below). It normally does not 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. If you want to include a
"]" in the set of characters, you must generally escape it.
However, if the "]" is the first (or the second if the first
character is a caret) character of a bracketed character
class, it does not denote the end of the class (as you
cannot have an empty class) and is 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 ].
Character Ranges
It is not uncommon to want to match a range of characters.
Luckily, instead of listing all the characters in the range,
one 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 are in the class. For instance, "[0-9]" matches any
ASCII digit, and "[a-m]" matches any lowercase letter from
the first half of the ASCII alphabet.
Note that the two characters on either side of the hyphen
are not necessary 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 will be. Furthermore, such ranges may lead
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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 cannot syntactically be
part of a range, for instance because it is the first or the
last character of the character class, or if it immediately
follows a range, the hyphen isn't special, and will be
considered a character that is to be matched literally. You
have to escape the hyphen with a backslash if you want to
have 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.
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).
Negation
It is also possible to instead list the characters you do
not want to match. You can do so by using a caret ("^") as
the first character in the character class. For instance,
"[^a-z]" matches a character that is not a lowercase ASCII
letter.
This syntax make 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 to have the caret as
one of the characters you want to match, you either have to
escape the caret, or not list it first.
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
You can put any backslash sequence character class (with the
exception of "\N") inside a bracketed character class, and
it will act just as if you put all the characters matched by
the backslash sequence inside the character class. For
instance, "[a-f\d]" will match any decimal digit, or any of
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the lowercase letters between 'a' and 'f' inclusive.
"\N" within a bracketed character class must be of the forms
"\N{name}" or "\N{U+wide hex char}", and NOT be the form
that matches non-newlines, for the 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. Thus, you can't say:
/[\p{Thai}-\d]/ # Wrong!
POSIX Character Classes
POSIX character classes have the form "[:class:]", where
class is name, and the "[:" and ":]" delimiters. POSIX
character classes only appear inside bracketed character
classes, and are a convenient and descriptive way of listing
a group of characters, though they currently suffer from
portability issues (see below and "Locale, EBCDIC, Unicode
and UTF-8").
Be careful about the syntax,
# Correct:
$string =~ /[[:alpha:]]/
# Incorrect (will warn):
$string =~ /[:alpha:]/
The latter pattern would be a character class consisting of
a colon, and the letters "a", "l", "p" and "h". 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:
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alpha Any alphabetical character ("[A-Za-z]").
alnum Any alphanumerical character. ("[A-Za-z0-9]")
ascii Any character in the ASCII character set.
blank A GNU extension, equal to a space or a horizontal tab ("\t").
cntrl Any control character. See Note [2] below.
digit Any decimal digit ("[0-9]"), equivalent to "\d".
graph Any printable character, excluding a space. See Note [3] below.
lower Any lowercase character ("[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. "\s" plus the vertical tab ("\cK").
upper Any uppercase character ("[A-Z]").
word A Perl extension ("[A-Za-z0-9_]"), equivalent to "\w".
xdigit Any hexadecimal digit ("[0-9a-fA-F]").
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, will only match 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}" will match
not just the ASCII alphabetic characters, but any character
in the entire Unicode character set that is considered to be
alphabetic.
(Each of the counterparts has various synonyms as well.
"Properties accessible through \p{} and \P{}" in
perluniprops lists all the synonyms, plus all the characters
matched by each of the ASCII-range properties. For example
"\p{AHex}" is a synonym for "\p{ASCII_Hex_Digit}", and any
"\p" property name can be prefixed with "Is" such as
"\p{IsAlpha}".)
Both the "\p" forms are unaffected by any locale that is in
effect, or whether the string is in UTF-8 format or not, or
whether the platform is EBCDIC or not. In contrast, the
POSIX character classes are affected. If the source string
is in UTF-8 format, the POSIX classes (with the exception of
"[[:punct:]]", see Note [5] below) behave like their "Full-
range" Unicode counterparts. If the source string is not in
UTF-8 format, and no locale is in effect, and the platform
is not EBCDIC, all the POSIX classes behave like their
ASCII-range counterparts. Otherwise, they behave based on
the rules of the locale or EBCDIC code page.
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It is proposed to change this behavior in a future release
of Perl so that the the UTF8ness of the source string will
be irrelevant to the behavior of the POSIX character
classes. This means they will always behave in strict
accordance with the official POSIX standard. That is, if
either locale or EBCDIC code page is present, they will
behave in accordance with those; if absent, the classes will
match only their ASCII-range counterparts. If you disagree
with this proposal, send email to "perl5-porters@perl.org".
[[:...:]] ASCII-range Full-range backslash Note
Unicode Unicode sequence
-----------------------------------------------------
alpha \p{PosixAlpha} \p{Alpha}
alnum \p{PosixAlnum} \p{Alnum}
ascii \p{ASCII}
blank \p{PosixBlank} \p{Blank} = [1]
\p{HorizSpace} \h [1]
cntrl \p{PosixCntrl} \p{Cntrl} [2]
digit \p{PosixDigit} \p{Digit} \d
graph \p{PosixGraph} \p{Graph} [3]
lower \p{PosixLower} \p{Lower}
print \p{PosixPrint} \p{Print} [4]
punct \p{PosixPunct} \p{Punct} [5]
\p{PerlSpace} \p{SpacePerl} \s [6]
space \p{PosixSpace} \p{Space} [6]
upper \p{PosixUpper} \p{Upper}
word \p{PerlWord} \p{Word} \w
xdigit \p{ASCII_Hex_Digit} \p{XDigit}
[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.
In the ASCII range, characters whose ordinals are
between 0 and 31 inclusive, plus 127 ("DEL") are control
characters.
On EBCDIC platforms, it is likely that the code page
will define "[[:cntrl:]]" to be the EBCDIC equivalents
of the ASCII controls, plus the controls that in Unicode
have ordinals from 128 through 159.
[3] Any character that is graphical, that is, visible. This
class consists of all the alphanumerical characters and
all punctuation characters.
[4] All printable characters, which is the set of all the
graphical characters plus whitespace characters that are
not also controls.
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[5] (punct)
"\p{PosixPunct}" and "[[:punct:]]" in the ASCII range
match all the non-controls, non-alphanumeric, non-space
characters: "[-!"#$%&'()*+,./:;<=>?@[\\\]^_`{|}~]"
(although if a locale is in effect, it could alter the
behavior of "[[:punct:]]").
"\p{Punct}" matches a somewhat different set in the
ASCII range, namely "[-!"#%&'()*,./:;?@[\\\]_{}]". That
is, it is missing "[$+<=>^`|~]". This is because
Unicode splits what POSIX considers to be punctuation
into two categories, Punctuation and Symbols.
When the matching string is in UTF-8 format,
"[[:punct:]]" matches what it 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 for a UTF-8 string,
"[[:punct:]]" matches all the characters that Unicode
considers to be punctuation, plus all the ASCII-range
characters that Unicode considers to be symbols.
[6] "\p{SpacePerl}" and "\p{Space}" differ only in that
"\p{Space}" additionally matches the vertical tab,
"\cK". Same for the two ASCII-only range forms.
Negation
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{Digit} \D
[[:^space:]] \P{PosixSpace} \P{Space}
\P{PerlSpace} \P{SpacePerl} \S
[[:^word:]] \P{PerlWord} \P{Word} \W
[= =] and [. .]
Perl will recognize the POSIX character classes "[=class=]",
and "[.class.]", but does not (yet?) support them. Use of
such a construct will lead to an error.
Examples
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/[[: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'. 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 result matches all
# characters except the letters 'a' to 'f' and
# 'A' to 'F'.
Locale, EBCDIC, Unicode and UTF-8
Some of the character classes have a somewhat different
behaviour depending on the internal encoding of the source
string, and the locale that is in effect, and if the program
is running on an EBCDIC platform.
"\w", "\d", "\s" and the POSIX character classes (and their
negations, including "\W", "\D", "\S") suffer from this
behaviour. (Since the backslash sequences "\b" and "\B" are
defined in terms of "\w" and "\W", they also are affected.)
The rule is that if the source string is in UTF-8 format,
the character classes match according to the Unicode
properties. If the source string isn't, then the character
classes match according to whatever locale or EBCDIC code
page is in effect. If there is no locale nor EBCDIC, they
match the ASCII defaults (0 to 9 for "\d"; 52 letters, 10
digits and underscore for "\w"; etc.).
This usually means that if you are matching against
characters whose "ord()" values are between 128 and 255
inclusive, your character class may match or not depending
on the current locale or EBCDIC code page, and whether the
source string is in UTF-8 format. The string will be in
UTF-8 format if it contains characters whose "ord()" value
exceeds 255. But a string may be in UTF-8 format without it
having such characters. See "The "Unicode Bug"" in
perlunicode.
For portability reasons, it may be better to not use "\w",
"\d", "\s" or the POSIX character classes, and use the
Unicode properties instead.
Examples
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Perl Programmers Reference Guide PERLRECHARCLASS(1)
$str = "\xDF"; # $str is not in UTF-8 format.
$str =~ /^\w/; # No match, as $str isn't in UTF-8 format.
$str .= "\x{0e0b}"; # Now $str is in UTF-8 format.
$str =~ /^\w/; # Match! $str is now in UTF-8 format.
chop $str;
$str =~ /^\w/; # Still a match! $str remains in UTF-8 format.
ATTRIBUTES
See attributes(5) for descriptions of the following
attributes:
+---------------+------------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+---------------+------------------+
|Availability | runtime/perl-512 |
+---------------+------------------+
|Stability | Uncommitted |
+---------------+------------------+
NOTES
This software was built from source available at
https://java.net/projects/solaris-userland. The original
community source was downloaded from
http://www.cpan.org/src/5.0/perl-5.12.5.tar.bz2
Further information about this software can be found on the
open source community website at http://www.perl.org/.
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