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-rw-r--r--Master/tlpkg/tlperl/lib/pods/perlrecharclass.pod596
1 files changed, 364 insertions, 232 deletions
diff --git a/Master/tlpkg/tlperl/lib/pods/perlrecharclass.pod b/Master/tlpkg/tlperl/lib/pods/perlrecharclass.pod
index a9b5ea37c74..b7526b45fae 100644
--- a/Master/tlpkg/tlperl/lib/pods/perlrecharclass.pod
+++ b/Master/tlpkg/tlperl/lib/pods/perlrecharclass.pod
@@ -44,7 +44,7 @@ Here are some examples:
"ab" =~ /^.$/ # No match (dot matches one character)
=head2 Backslash sequences
-X<\w> X<\W> X<\s> X<\S> X<\d> X<\D> X<\p> X<\P>
+X<\w> X<\W> X<\s> X<\S> X<\d> X<\D> X<\p> X<\P>
X<\N> X<\v> X<\V> X<\h> X<\H>
X<word> X<whitespace>
@@ -74,57 +74,104 @@ character classes, see L<perlrebackslash>.)
=head3 Digits
-C<\d> matches a single character that is considered to be a decimal I<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, C<\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, C<\d> matches just the digits '0' to '9'.
-See L</Locale, EBCDIC, Unicode and UTF-8>.
-
-Unicode digits may cause some confusion, and some security issues. In UTF-8
-strings, C<\d> matches the same characters matched by
-C<\p{General_Category=Decimal_Number}>, or synonymously,
-C<\p{General_Category=Digit}>. Starting with Unicode version 4.1, this is the
-same set of characters matched by C<\p{Numeric_Type=Decimal}>.
-
+C<\d> matches a single character considered to be a decimal I<digit>.
+If the C</a> modifier in effect, it matches [0-9]. Otherwise, it
+matches anything that is matched by C<\p{Digit}>, which includes [0-9].
+(An unlikely possible exception is that under locale matching rules, the
+current locale might not have [0-9] matched by C<\d>, and/or might match
+other characters whose code point is less than 256. Such a locale
+definition 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 C</a> modifier is in effect C<\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 C<\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). An application that
+is expecting only the ASCII digits might be misled, or if the match is
+C<\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. L<Unicode::UCD/num()> can be used to safely
+calculate the value, returning C<undef> if the input string contains
+such a mixture.
+
+What C<\p{Digit}> means (and hence C<\d> except under the C</a>
+modifier) is C<\p{General_Category=Decimal_Number}>, or synonymously,
+C<\p{General_Category=Digit}>. Starting with Unicode version 4.1, this
+is the same set of characters matched by C<\p{Numeric_Type=Decimal}>.
But Unicode also has a different property with a similar name,
C<\p{Numeric_Type=Digit}>, which matches a completely different set of
-characters. These characters are things such as subscripts.
-
-The design intent is for C<\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 10",
-"times 100", etc. (See L<http://www.unicode.org/notes/tn21>.)
+characters. These characters are things such as C<CIRCLED DIGIT ONE>
+or subscripts, or are from writing systems that lack all ten digits.
-Some of the non-European digits that C<\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).
+The design intent is for C<\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",
+C<\p{Numeric_Type=Digit}>, and so C<\d> doesn't match them.
-It may be useful for security purposes for an application to require that all
-digits in a row be from the same script. See L<Unicode::UCD/charscript()>.
+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 10", "times 100",
+etc. (See L<http://www.unicode.org/notes/tn21>.)
-Any character that isn't matched by C<\d> will be matched by C<\D>.
+Any character not matched by C<\d> is matched by C<\D>.
=head3 Word characters
A C<\w> matches a single alphanumeric character (an alphabetic character, or a
-decimal digit) or an underscore (C<_>), not a whole word. To match a whole
-word, use C<\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, C<\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, C<\w> matches those characters that are considered word characters by
-the current locale or EBCDIC code page. Without a locale or EBCDIC code page,
-C<\w> matches the ASCII letters, digits and the underscore.
-See L</Locale, EBCDIC, Unicode and UTF-8>.
+decimal digit) or a connecting punctuation character, such as an
+underscore ("_"). It does not match a whole word. To match a whole
+word, use C<\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.
+
+=over
+
+=item If the C</a> modifier is in effect ...
+
+C<\w> matches the 63 characters [a-zA-Z0-9_].
+
+=item otherwise ...
+
+=over
+
+=item For code points above 255 ...
+
+C<\w> matches the same as C<\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 C<COMBINING TILDE> and the modifier letters, which
+are generally used to add auxiliary markings to letters.
+
+=item For code points below 256 ...
+
+=over
+
+=item if locale rules are in effect ...
+
+C<\w> matches the platform's native underscore character plus whatever
+the locale considers to be alphanumeric.
+
+=item if Unicode rules are in effect or if on an EBCDIC platform ...
+
+C<\w> matches exactly what C<\p{Word}> matches.
+
+=item otherwise ...
+
+C<\w> matches [a-zA-Z0-9_].
+
+=back
+
+=back
+
+=back
+
+Which rules apply are determined as described in L<perlre/Which character set modifier is in effect?>.
There are a number of security issues with the full Unicode list of word
characters. See L<http://unicode.org/reports/tr36>.
@@ -134,36 +181,68 @@ 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 L<http://unicode.org/reports/tr31>.
-Any character that isn't matched by C<\w> will be matched by C<\W>.
+Any character not matched by C<\w> is matched by C<\W>.
=head3 Whitespace
-C<\s> matches any single character that is considered whitespace. The exact
-set of characters matched by C<\s> depends on whether the source string is in
-UTF-8 format and the locale or EBCDIC code page that is in effect. If it's in
-UTF-8 format, C<\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, C<\s> matches whatever is considered
-whitespace by the current locale or EBCDIC code page. Without a locale or
-EBCDIC code page, C<\s> matches the horizontal tab (C<\t>), the newline
-(C<\n>), the form feed (C<\f>), the carriage return (C<\r>), and the space.
-(Note that it doesn't match the vertical tab, C<\cK>.) Perhaps the most notable
-possible surprise is that C<\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 L</Locale, EBCDIC, Unicode and UTF-8>.
-
-Any character that isn't matched by C<\s> will be matched by C<\S>.
-
-C<\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. C<\H> will match any character
-that is not considered horizontal whitespace.
-
-C<\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.
-C<\V> will match any character that is not considered vertical whitespace.
+C<\s> matches any single character considered whitespace.
+
+=over
+
+=item If the C</a> modifier is in effect ...
+
+C<\s> matches the 5 characters [\t\n\f\r ]; that is, the horizontal tab,
+the newline, the form feed, the carriage return, and the space. (Note
+that it doesn't match the vertical tab, C<\cK> on ASCII platforms.)
+
+=item otherwise ...
+
+=over
+
+=item For code points above 255 ...
+
+C<\s> matches exactly the code points above 255 shown with an "s" column
+in the table below.
+
+=item For code points below 256 ...
+
+=over
+
+=item if locale rules are in effect ...
+
+C<\s> matches whatever the locale considers to be whitespace. Note that
+this is likely to include the vertical space, unlike non-locale C<\s>
+matching.
+
+=item if Unicode rules are in effect or if on an EBCDIC platform ...
+
+C<\s> matches exactly the characters shown with an "s" column in the
+table below.
+
+=item otherwise ...
+
+C<\s> matches [\t\n\f\r ].
+Note that this list doesn't include the non-breaking space.
+
+=back
+
+=back
+
+=back
+
+Which rules apply are determined as described in L<perlre/Which character set modifier is in effect?>.
+
+Any character not matched by C<\s> is matched by C<\S>.
+
+C<\h> matches any character considered horizontal whitespace;
+this includes the space and tab characters and several others
+listed in the table below. C<\H> matches any character
+not considered horizontal whitespace.
+
+C<\v> matches any character considered vertical whitespace;
+this includes the carriage return and line feed characters (newline)
+plus several other characters, all listed in the table below.
+C<\V> matches any character not considered vertical whitespace.
C<\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
@@ -171,22 +250,16 @@ sequence. Therefore, it cannot be used inside a bracketed character
class; use C<\v> instead (vertical whitespace).
Details are discussed in L<perlrebackslash>.
-Note that unlike C<\s>, C<\d> and C<\w>, C<\h> and C<\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.
+Note that unlike C<\s> (and C<\d> and C<\w>), C<\h> and C<\v> always match
+the same characters, without regard to other factors, such as whether the
+source string is in UTF-8 format.
-One might think that C<\s> is equivalent to C<[\h\v]>. This is not true. The
-vertical tab (C<"\x0b">) is not matched by C<\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 C<"\x85">) and the no-break space (ASCII-platform
-C<"\xA0">) characters are not matched by C<\s>, but are by C<\v> and C<\h>
-respectively. If the source string is in UTF-8 format, both the next line and
-the no-break space are matched by C<\s>.
+One might think that C<\s> is equivalent to C<[\h\v]>. This is not true.
+For example, the vertical tab (C<"\x0b">) is not matched by C<\s>, it is
+however considered vertical whitespace.
The following table is a complete listing of characters matched by
-C<\s>, C<\h> and C<\v> as of Unicode 5.2.
+C<\s>, C<\h> and C<\v> as of Unicode 6.0.
The first column gives the code point of the character (in hex format),
the second column gives the (Unicode) name. The third column indicates
@@ -224,18 +297,15 @@ page is in effect that changes the C<\s> matching).
=item [1]
-NEXT LINE and NO-BREAK SPACE only match C<\s> if the source string is in
-UTF-8 format, or the locale or EBCDIC code page that is in effect includes them.
+NEXT LINE and NO-BREAK SPACE may or may not match C<\s> depending
+on the rules in effect. See
+L<the beginning of this section|/Whitespace>.
=back
-It is worth noting that C<\d>, C<\w>, etc, match single characters, not
-complete numbers or words. To match a number (that consists of integers),
-use C<\d+>; to match a word, use C<\w+>.
-
=head3 \N
-C<\N> is new in 5.12, and is experimental. It, like the dot, will match any
+C<\N> is new in 5.12, and is experimental. It, like the dot, matches any
character that is not a newline. The difference is that C<\N> is not influenced
by the I<single line> regular expression modifier (see L</The dot> above). Note
that the form C<\N{...}> may mean something completely different. When the
@@ -245,7 +315,7 @@ non-newlines; C<\N{5,}> means to match 5 or more non-newlines. But if C<{...}>
is not a legal quantifier, it is presumed to be a named character. See
L<charnames> for those. For example, none of C<\N{COLON}>, C<\N{4F}>, and
C<\N{F4}> contain legal quantifiers, so Perl will try to find characters whose
-names are, respectively, C<COLON>, C<4F>, and C<F4>.
+names are respectively C<COLON>, C<4F>, and C<F4>.
=head3 Unicode Properties
@@ -254,7 +324,7 @@ Unicode properties. One letter property names can be used in the C<\pP> form,
with the property name following the C<\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 C<\p{name=value}>,
-which means to match if the property "name" for the character has the particular
+which means to match if the property "name" for the character has that particular
"value".
For instance, a match for a number can be written as C</\pN/> or as
C</\p{Number}/>, or as C</\p{Number=True}/>.
@@ -266,13 +336,37 @@ C</\pLl/> is valid, but means something different.
It matches a two character string: a letter (Unicode property C<\pL>),
followed by a lowercase C<l>.
-For more details, see L<perlunicode/Unicode Character Properties>; for a
+If neither the C</a> modifier nor locale rules are in effect, the use of
+a Unicode property will force the regular expression into using Unicode
+rules.
+
+Note that almost all properties are immune to case-insensitive matching.
+That is, adding a C</i> regular expression modifier does not change what
+they match. There are two sets that are affected. The first set is
+C<Uppercase_Letter>,
+C<Lowercase_Letter>,
+and C<Titlecase_Letter>,
+all of which match C<Cased_Letter> under C</i> matching.
+The second set is
+C<Uppercase>,
+C<Lowercase>,
+and C<Titlecase>,
+all of which match C<Cased> under C</i> matching.
+(The difference between these sets is that some things, such as Roman
+Numerals, come in both upper and lower case so they are C<Cased>, but
+aren't considered to be letters, so they aren't C<Cased_Letter>s. They're
+actually C<Letter_Number>s.)
+This set also includes its subsets C<PosixUpper> and C<PosixLower>, both
+of which under C</i> matching match C<PosixAlpha>.
+
+For more details on Unicode properties, see L<perlunicode/Unicode
+Character Properties>; for a
complete list of possible properties, see
-L<perluniprops/Properties accessible through \p{} and \P{}>.
+L<perluniprops/Properties accessible through \p{} and \P{}>,
+which notes all forms that have C</i> differences.
It is also possible to define your own properties. This is discussed in
L<perlunicode/User-Defined Character Properties>.
-
=head4 Examples
"a" =~ /\w/ # Match, "a" is a 'word' character.
@@ -296,6 +390,10 @@ L<perlunicode/User-Defined Character Properties>.
# Thai Unicode class.
"a" =~ /\P{Lao}/ # Match, as "a" is not a Laotian character.
+It is worth emphasizing that C<\d>, C<\w>, etc, match single characters, not
+complete numbers or words. To match a number (that consists of digits),
+use C<\d+>; to match a word, use C<\w+>. But be aware of the security
+considerations in doing so, as mentioned above.
=head2 Bracketed Character Classes
@@ -303,10 +401,10 @@ 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: C<[aeiou]>.
This matches one of C<a>, C<e>, C<i>, C<o> or C<u>. Like the other
-character classes, exactly one character will be matched. To match
+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 L<quantifier|perlre/Quantifiers>. For
-instance, C<[aeiou]+> matches a string of one or more lowercase English vowels.
+instance, C<[aeiou]+> matches 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.
@@ -319,6 +417,19 @@ Examples:
# a single character.
"ae" =~ /^[aeiou]+$/ # Match, due to the quantifier.
+ -------
+
+* There is an exception to a bracketed character class matching only a
+single character. When the class is to match caselessely under C</i>
+matching rules, and a character inside the class matches a
+multiple-character sequence caselessly under Unicode rules, the class
+(when not L<inverted|/Negation>) will also match that sequence. For
+example, Unicode says that the letter C<LATIN SMALL LETTER SHARP S>
+should match the sequence C<ss> under C</i> rules. Thus,
+
+ 'ss' =~ /\A\N{LATIN SMALL LETTER SHARP S}\z/i # Matches
+ 'ss' =~ /\A[aeioust\N{LATIN SMALL LETTER SHARP S}]\z/i # Matches
+
=head3 Special Characters Inside a Bracketed Character Class
Most characters that are meta characters in regular expressions (that
@@ -346,13 +457,15 @@ C<\e>,
C<\f>,
C<\n>,
C<\N{I<NAME>}>,
-C<\N{U+I<wide hex char>}>,
+C<\N{U+I<hex char>}>,
C<\r>,
C<\t>,
and
C<\x>
-are also special and have the same meanings as they do outside a bracketed character
-class.
+are also special and have the same meanings as they do outside a
+bracketed character class. (However, inside a bracketed character
+class, if C<\N{I<NAME>}> expands to a sequence of characters, only the first
+one in the sequence is used, with a warning.)
Also, a backslash followed by two or three octal digits is considered an octal
number.
@@ -365,6 +478,7 @@ A C<]> is normally either the end of a POSIX character class (see
L</POSIX Character Classes> below), or it signals the end of the bracketed
character class. If you want to include a C<]> in the set of characters, you
must generally escape it.
+
However, if the C<]> is the I<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)
@@ -385,26 +499,26 @@ Examples:
=head3 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 (C<->).
+of listing all characters in the range, one may use the hyphen (C<->).
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
+by a hyphen, it's treated as if all characters between the two were in
the class. For instance, C<[0-9]> matches any ASCII digit, and C<[a-m]>
-matches any lowercase letter from the first half of the ASCII alphabet.
+matches any lowercase letter from the first half of the old 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,
+necessarily both letters or both digits. Any character is possible,
although not advisable. C<['-?]> contains a range of characters, but
-most people will not know which characters that will be. Furthermore,
+most people will not know which characters that means. 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 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.
+or if it immediately follows a range, the hyphen isn't special, and so is
+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.
Examples:
@@ -422,13 +536,27 @@ Examples:
It is also possible to instead list the characters you do not want to
match. You can do so by using a caret (C<^>) as the first character in the
-character class. For instance, C<[^a-z]> matches a character that is not a
-lowercase ASCII letter.
+character class. For instance, C<[^a-z]> matches any character that is not a
+lowercase ASCII letter, which therefore includes almost a hundred thousand
+Unicode letters. The class is said to be "negated" or "inverted".
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.
+the caret as one of the characters to match, either escape the caret or
+else not list it first.
+
+In inverted bracketed character classes, Perl ignores the Unicode rules
+that normally say that a given character matches a sequence of multiple
+characters under caseless C</i> matching, which otherwise could be
+highly confusing:
+
+ "ss" =~ /^[^\xDF]+$/ui;
+
+This should match any sequences of characters that aren't C<\xDF> nor
+what C<\xDF> matches under C</i>. C<"s"> isn't C<\xDF>, but Unicode
+says that C<"ss"> is what C<\xDF> matches under C</i>. So which one
+"wins"? Do you fail the match because the string has C<ss> or accept it
+because it has an C<s> followed by another C<s>?
Examples:
@@ -440,13 +568,13 @@ Examples:
=head3 Backslash Sequences
You can put any backslash sequence character class (with the exception of
-C<\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, C<[a-f\d]> will match any decimal digit, or any
+C<\N> and C<\R>) inside a bracketed character class, and it will act just
+as if you had put all characters matched by the backslash sequence inside the
+character class. For instance, C<[a-f\d]> matches any decimal digit, or any
of the lowercase letters between 'a' and 'f' inclusive.
C<\N> within a bracketed character class must be of the forms C<\N{I<name>}>
-or C<\N{U+I<wide hex char>}>, and NOT be the form that matches non-newlines,
+or C<\N{U+I<hex char>}>, and NOT be the form that matches non-newlines,
for the same reason that a dot C<.> inside a bracketed character class loses
its special meaning: it matches nearly anything, which generally isn't what you
want to happen.
@@ -472,8 +600,7 @@ X<lower> X<print> X<punct> X<space> X<upper> X<word> X<xdigit>
POSIX character classes have the form C<[:class:]>, where I<class> is
name, and the C<[:> and C<:]> delimiters. POSIX character classes only appear
I<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 L<Locale, EBCDIC, Unicode and UTF-8>).
+way of listing a group of characters.
Be careful about the syntax,
@@ -485,8 +612,8 @@ Be careful about the syntax,
The latter pattern would be a character class consisting of a colon,
and the letters C<a>, C<l>, C<p> and C<h>.
-POSIX character classes can be part of a larger bracketed character class. For
-example,
+POSIX character classes can be part of a larger bracketed character class.
+For example,
[01[:alpha:]%]
@@ -495,7 +622,7 @@ is valid and matches '0', '1', any alphabetic character, and the percent sign.
Perl recognizes the following POSIX character classes:
alpha Any alphabetical character ("[A-Za-z]").
- alnum Any alphanumerical character. ("[A-Za-z0-9]")
+ alnum Any alphanumeric 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.
@@ -515,57 +642,93 @@ 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 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,
-C<\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.
+C<\p{Alpha}> matches not just the ASCII alphabetic characters, but any
+character in the entire Unicode character set considered alphabetic.
+The column labelled "backslash sequence" is a (short) synonym for
+the Full-range Unicode form.
(Each of the counterparts has various synonyms as well.
-L<perluniprops/Properties accessible through \p{} and \P{}> lists all the
-synonyms, plus all the characters matched by each of the ASCII-range
-properties. For example C<\p{AHex}> is a synonym for C<\p{ASCII_Hex_Digit}>,
+L<perluniprops/Properties accessible through \p{} and \P{}> lists all
+synonyms, plus all characters matched by each ASCII-range property.
+For example, C<\p{AHex}> is a synonym for C<\p{ASCII_Hex_Digit}>,
and any C<\p> property name can be prefixed with "Is" such as C<\p{IsAlpha}>.)
-Both the C<\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 C<[[: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.
-
-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 C<perl5-porters@perl.org>.
-
- [[:...:]] ASCII-range Full-range backslash Note
- Unicode Unicode sequence
+Both the C<\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:
+
+=over
+
+=item If the C</a> modifier, is in effect ...
+
+Each of the POSIX classes matches exactly the same as their ASCII-range
+counterparts.
+
+=item otherwise ...
+
+=over
+
+=item For code points above 255 ...
+
+The POSIX class matches the same as its Full-range counterpart.
+
+=item For code points below 256 ...
+
+=over
+
+=item if locale rules are in effect ...
+
+The POSIX class matches according to the locale.
+
+=item if Unicode rules are in effect or if on an EBCDIC platform ...
+
+The POSIX class matches the same as the Full-range counterpart.
+
+=item otherwise ...
+
+The POSIX class matches the same as the ASCII range counterpart.
+
+=back
+
+=back
+
+=back
+
+Which rules apply are determined as described in
+L<perlre/Which character set modifier is in effect?>.
+
+It is proposed to change this behavior in a future release of Perl so that
+whether or not Unicode rules are in effect would not change the
+behavior: Outside of locale or an EBCDIC code page, the POSIX classes
+would behave like their ASCII-range counterparts. If you wish to
+comment on this proposal, send email to C<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}
+ 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}
=over 4
@@ -576,51 +739,59 @@ C<\p{Blank}> and C<\p{HorizSpace}> are synonyms.
=item [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,
+the terminal somehow: for example, newline and backspace are control characters.
+In the ASCII range, characters whose code points are between 0 and 31 inclusive,
plus 127 (C<DEL>) are control characters.
On EBCDIC platforms, it is likely that the code page will define C<[[:cntrl:]]>
to be the EBCDIC equivalents of the ASCII controls, plus the controls
-that in Unicode have ordinals from 128 through 159.
+that in Unicode have code pointss from 128 through 159.
=item [3]
Any character that is I<graphical>, that is, visible. This class consists
-of all the alphanumerical characters and all punctuation characters.
+of all alphanumeric characters and all punctuation characters.
=item [4]
-All printable characters, which is the set of all the graphical characters
-plus whitespace characters that are not also controls.
+All printable characters, which is the set of all graphical characters
+plus those whitespace characters which are not also controls.
-=item [5] (punct)
+=item [5]
-C<\p{PosixPunct}> and C<[[:punct:]]> in the ASCII range match all the
+C<\p{PosixPunct}> and C<[[:punct:]]> in the ASCII range match all
non-controls, non-alphanumeric, non-space characters:
C<[-!"#$%&'()*+,./:;<=E<gt>?@[\\\]^_`{|}~]> (although if a locale is in effect,
it could alter the behavior of C<[[:punct:]]>).
-C<\p{Punct}> matches a somewhat different set in the ASCII range, namely
+The similarly named property, C<\p{Punct}>, matches a somewhat different
+set in the ASCII range, namely
C<[-!"#%&'()*,./:;?@[\\\]_{}]>. That is, it is missing C<[$+E<lt>=E<gt>^`|~]>.
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, C<[[:punct:]]> matches what it
-matches in the ASCII range, plus what C<\p{Punct}> matches. This is different
-than strictly matching according to C<\p{Punct}>. Another way to say it is that
-for a UTF-8 string, C<[[:punct:]]> matches all the characters that Unicode
-considers to be punctuation, plus all the ASCII-range characters that Unicode
-considers to be symbols.
+C<\p{XPosixPunct}> and (in Unicode mode) C<[[:punct:]]>, match what
+C<\p{PosixPunct}> matches in the ASCII range, plus what C<\p{Punct}>
+matches. This is different than strictly matching according to
+C<\p{Punct}>. Another way to say it is that
+if Unicode rules are in effect, C<[[:punct:]]> matches all characters
+that Unicode considers punctuation, plus all ASCII-range characters that
+Unicode considers symbols.
=item [6]
-C<\p{SpacePerl}> and C<\p{Space}> differ only in that C<\p{Space}> additionally
+C<\p{SpacePerl}> and C<\p{Space}> differ only in that in non-locale
+matching, C<\p{Space}> additionally
matches the vertical tab, C<\cK>. Same for the two ASCII-only range forms.
=back
-=head4 Negation
+There are various other synonyms that can be used for these besides
+C<\p{HorizSpace}> and \C<\p{XPosixBlank}>. For example,
+C<\p{PosixAlpha}> can be written as C<\p{Alpha}>. All are listed
+in L<perluniprops/Properties accessible through \p{} and \P{}>.
+
+=head4 Negation of POSIX character classes
X<character class, negation>
A Perl extension to the POSIX character class is the ability to
@@ -630,17 +801,19 @@ 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
+ [[:^digit:]] \P{PosixDigit} \P{XPosixDigit} \D
+ [[:^space:]] \P{PosixSpace} \P{XPosixSpace}
+ \P{PerlSpace} \P{XPerlSpace} \S
+ [[:^word:]] \P{PerlWord} \P{XPosixWord} \W
-=head4 [= =] and [. .]
+The backslash sequence can mean either ASCII- or Full-range Unicode,
+depending on various factors as described in L<perlre/Which character set modifier is in effect?>.
-Perl will recognize the POSIX character classes C<[=class=]>, and
-C<[.class.]>, but does not (yet?) support them. Use of
-such a construct will lead to an error.
+=head4 [= =] and [. .]
+Perl recognizes the POSIX character classes C<[=class=]> and
+C<[.class.]>, but does not (yet?) support them. Any attempt to use
+either construct raises an exception.
=head4 Examples
@@ -656,44 +829,3 @@ such a construct will lead to an error.
# hex digit. The result matches all
# characters except the letters 'a' to 'f' and
# 'A' to 'F'.
-
-
-=head2 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.
-
-C<\w>, C<\d>, C<\s> and the POSIX character classes (and their negations,
-including C<\W>, C<\D>, C<\S>) suffer from this behaviour. (Since the backslash
-sequences C<\b> and C<\B> are defined in terms of C<\w> and C<\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 C<\d>; 52 letters, 10 digits and underscore for C<\w>;
-etc.).
-
-This usually means that if you are matching against characters whose C<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 C<ord()> value exceeds 255. But a string may be in
-UTF-8 format without it having such characters. See L<perlunicode/The
-"Unicode Bug">.
-
-For portability reasons, it may be better to not use C<\w>, C<\d>, C<\s>
-or the POSIX character classes, and use the Unicode properties instead.
-
-=head4 Examples
-
- $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.
-
-=cut