\l Lowercase next character.
\L Lowercase till \E.
\n (Logical) newline character.
+ \N Any character but newline.
\N{} Named (Unicode) character.
\p{}, \pP Character with a Unicode property.
\P{}, \PP Character without a Unicode property.
Octal escapes consist of a backslash followed by two or three octal digits
matching the code point of the character you want to use. This allows for
-522 characters (C<\00> up to C<\777>) that can be expressed this way.
+512 characters (C<\00> up to C<\777>) that can be expressed this way.
Enough in pre-Unicode days, but most Unicode characters cannot be escaped
this way.
=item 1
-If the backslash is followed by a single digit, it's a backrefence.
+If the backslash is followed by a single digit, it's a backreference.
=item 2
C<\w> is a character class that matches any I<word> character (letters,
digits, underscore). C<\d> is a character class that matches any digit,
while the character class C<\s> matches any white space character.
-New in perl 5.10 are the classes C<\h> and C<\v> which match horizontal
+New in perl 5.10.0 are the classes C<\h> and C<\v> which match horizontal
and vertical white space characters.
The uppercase variants (C<\W>, C<\D>, C<\S>, C<\H>, and C<\V>) are
=head3 Relative referencing
-New in perl 5.10 is different way of referring to capture buffers: C<\g>.
+New in perl 5.10.0 is a different way of referring to capture buffers: C<\g>.
C<\g> takes a number as argument, with the number in curly braces (the
braces are optional). If the number (N) does not have a sign, it's a reference
to the Nth capture group (so C<\g{2}> is equivalent to C<\2> - except that
=head3 Named referencing
-Also new in perl 5.10 is the use of named capture buffers, which can be
+Also new in perl 5.10.0 is the use of named capture buffers, which can be
referred to by name. This is done with C<\g{name}>, which is a
backreference to the capture buffer with the name I<name>.
=item \K
-This is new in perl 5.10. Anything that is matched left of C<\K> is
+This is new in perl 5.10.0. Anything that is matched left of C<\K> is
not included in C<$&> - and will not be replaced if the pattern is
used in a substitution. This will allow you to write C<s/PAT1 \K PAT2/REPL/x>
instead of C<s/(PAT1) PAT2/${1}REPL/x> or C<s/(?<=PAT1) PAT2/REPL/x>.
the newline used in Windows text files). C<\R> is equivalent with
C<< (?>\x0D\x0A)|\v) >>. Since C<\R> can match a more than one character,
it cannot be put inside a bracketed character class; C</[\R]/> is an error.
-C<\R> is introduced in perl 5.10.
+C<\R> was introduced in perl 5.10.0.
-Mnemonic: none really. C<\R> was picked because PCRE already uses C<\R>.
+Mnemonic: none really. C<\R> was picked because PCRE already uses C<\R>,
+and more importantly because Unicode recommends such a regular expression
+metacharacter, and suggests C<\R> as the notation.
=item \X
include (but are not restricted to) I<combining characters> and
I<vowel signs>.
+C<\X> matches quite well what normal (non-Unicode-programmer) usage
+would consider a single character: for example a base character
+(the C<\PM> above), for example a letter, followed by zero or more
+diacritics, which are I<combining characters> (the C<\pM*> above).
+
Mnemonic: eI<X>tended Unicode character.
=back
projects / p5sagit/p5-mst-13.2.git / blobdiff