/(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
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.
-Here is the list as of Unicode 3.1.0 (the two-letter classes) and
-Perl 5.8.0 (the one-letter classes):
-
- L Letter
- Lu Letter, Uppercase
- Ll Letter, Lowercase
- Lt Letter, Titlecase
- Lm Letter, Modifier
- Lo Letter, Other
- M Mark
- Mn Mark, Non-Spacing
- Mc Mark, Spacing Combining
- Me Mark, Enclosing
- N Number
- Nd Number, Decimal Digit
- Nl Number, Letter
- No Number, Other
- P Punctuation
- Pc Punctuation, Connector
- Pd Punctuation, Dash
- Ps Punctuation, Open
- Pe Punctuation, Close
- Pi Punctuation, Initial quote
- (may behave like Ps or Pe depending on usage)
- Pf Punctuation, Final quote
- (may behave like Ps or Pe depending on usage)
- Po Punctuation, Other
- S Symbol
- Sm Symbol, Math
- Sc Symbol, Currency
- Sk Symbol, Modifier
- So Symbol, Other
- Z Separator
- Zs Separator, Space
- Zl Separator, Line
- Zp Separator, Paragraph
- C Other
- Cc Other, Control
- Cf Other, Format
- Cs Other, Surrogate
- Co Other, Private Use
- Cn Other, Not Assigned (Unicode defines no Cn characters)
-
-Additionally, because scripts differ in their directionality
-(for example Hebrew is written right to left), all characters
-have their directionality defined:
-
- BidiL Left-to-Right
- BidiLRE Left-to-Right Embedding
- BidiLRO Left-to-Right Override
- BidiR Right-to-Left
- BidiAL Right-to-Left Arabic
- BidiRLE Right-to-Left Embedding
- BidiRLO Right-to-Left Override
- BidiPDF Pop Directional Format
- BidiEN European Number
- BidiES European Number Separator
- BidiET European Number Terminator
- BidiAN Arabic Number
- BidiCS Common Number Separator
- BidiNSM Non-Spacing Mark
- BidiBN Boundary Neutral
- BidiB Paragraph Separator
- BidiS Segment Separator
- BidiWS Whitespace
- BidiON Other Neutrals
-
-For the the full and latest information see the latest Unicode standard.
+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>,
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