/(ab(cd|ef)((gi)|j))/;
1 2 34
-so that if the regexp matched, e.g., C<$2> would contain 'cd' or 'ef'.
-For convenience, perl sets C<$+> to the highest numbered C<$1>, C<$2>,
-... that got assigned.
+so that if the regexp matched, e.g., C<$2> would contain 'cd' or 'ef'. For
+convenience, perl sets C<$+> to the string held by the highest numbered
+C<$1>, C<$2>, ... that got assigned (and, somewhat related, C<$^N> to the
+value of the C<$1>, C<$2>, ... most-recently assigned; i.e. the C<$1>,
+C<$2>, ... associated with the rightmost closing parenthesis used in the
+match).
Closely associated with the matching variables C<$1>, C<$2>, ... are
the B<backreferences> C<\1>, C<\2>, ... . Backreferences are simply
much fun as programming in machine code. So another way to specify
Unicode characters is to use the S<B<named character> > escape
sequence C<\N{name}>. C<name> is a name for the Unicode character, as
-specified in the Unicode standard, or "U+" followed by the hexadecimal
-code of the character. For instance, if we wanted to represent or
-match the astrological sign for the planet Mercury, we could use
+specified in the Unicode standard. For instance, if we wanted to
+represent or match the astrological sign for the planet Mercury, we
+could use
use utf8; # We will be doing Unicode processing
use charnames ":full"; # use named chars with Unicode full names
print "\N{sigma} is Greek sigma\n";
A list of full names is found in the file Names.txt in the
-lib/perl5/5.6.0/unicode directory.
+lib/perl5/5.X.X/unicore directory.
The answer to requirement 2), as of 5.6.0, is that if a regexp
contains Unicode characters, the string is searched as a sequence of
$x =~ /^\p{IsLower}/; # doesn't match, lowercase char class
$x =~ /^\P{IsLower}/; # matches, char class sans lowercase
-If a C<name> is just one letter, the braces can be dropped. For
-instance, C<\pM> is the character class of Unicode 'marks'. Here is
-the association between some Perl named classes and the traditional
-Unicode classes:
+Here is the association between some Perl named classes and the
+traditional Unicode classes:
- Perl class name Unicode class name
+ Perl class name Unicode class name or regular expression
- IsAlpha Lu, Ll, or Lo
- IsAlnum Lu, Ll, Lo, or Nd
- IsASCII $code le 127
- IsCntrl C
+ IsAlpha /^[LM]/
+ IsAlnum /^[LMN]/
+ IsASCII $code <= 127
+ IsCntrl /^C/
+ IsBlank $code =~ /^(0020|0009)$/ || /^Z[^lp]/
IsDigit Nd
- IsGraph [^C] and $code ne "0020"
+ IsGraph /^([LMNPS]|Co)/
IsLower Ll
- IsPrint [^C]
- IsPunct P
- IsSpace Z, or ($code lt "0020" and chr(hex $code) is a \s)
- IsUpper Lu
- IsWord Lu, Ll, Lo, Nd or $code eq "005F"
+ IsPrint /^([LMNPS]|Co|Zs)/
+ IsPunct /^P/
+ IsSpace /^Z/ || ($code =~ /^(0009|000A|000B|000C|000D)$/
+ IsSpacePerl /^Z/ || ($code =~ /^(0009|000A|000C|000D)$/
+ IsUpper /^L[ut]/
+ IsWord /^[LMN]/ || $code eq "005F"
IsXDigit $code =~ /^00(3[0-9]|[46][1-6])$/
-For a full list of Perl class names, consult the mktables.PL program
-in the lib/perl5/5.6.0/unicode directory.
+You can also use the official Unicode class names with the C<\p> and
+C<\P>, like C<\p{L}> for Unicode 'letters', or C<\p{Lu}> for uppercase
+letters, or C<\P{Nd}> for non-digits. If a C<name> is just one
+letter, the braces can be dropped. For instance, C<\pM> is the
+character class of Unicode 'marks', for example accent marks.
+For the full list see L<perlunicode>.
+
+The Unicode has also been separated into various sets of charaters
+which you can test with C<\p{In...}> (in) and C<\P{In...}> (not in),
+for example C<\p{InLatin}>, C<\p{InGreek}>, or C<\P{InKatakana}>.
+For the full list see L<perlunicode>.
C<\X> is an abbreviation for a character class sequence that includes
the Unicode 'combining character sequences'. A 'combining character
atop it, as in the word Angstrom. C<\X> is equivalent to C<\PM\pM*}>,
i.e., a non-mark followed by one or more marks.
+For the the full and latest information about Unicode see the latest
+Unicode standard, or the Unicode Consortium's website http://www.unicode.org/
+
As if all those classes weren't enough, Perl also defines POSIX style
character classes. These have the form C<[:name:]>, with C<name> the
name of the POSIX class. The POSIX classes are C<alpha>, C<alnum>,