have warnings turned on, Perl will issue a warning if you use such a sequence.
[1].
-It is however garanteed that backslash or escape sequences never have a
+It is however guaranteed that backslash or escape sequences never have a
punctuation character following the backslash, not now, and not in a future
version of Perl 5. So it is safe to put a backslash in front of a non-word
character.
\s Character class for white space.
\S Character class for non white space.
\t Tab character.
- \u Uppercase next character.
+ \u Titlecase next character.
\U Uppercase till \E.
\v Character class for vertical white space.
\V Character class for non vertical white space.
=head3 Fixed characters
-A handful of characters have a dedidated I<character escape>. The following
+A handful of characters have a dedicated I<character escape>. The following
table shows them, along with their code points (in decimal and hex), their
ASCII name, the control escape (see below) and a short description.
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
A number of backslash sequences have to do with changing the character,
or characters following them. C<\l> will lowercase the character following
-it, while C<\u> will uppercase the character following it. (They perform
-similar functionality as the functions C<lcfirst> and C<ucfirst>).
+it, while C<\u> will uppercase (or, more accurately, titlecase) the
+character following it. (They perform similar functionality as the
+functions C<lcfirst> and C<ucfirst>).
To uppercase or lowercase several characters, one might want to use
C<\L> or C<\U>, which will lowercase/uppercase all characters following
-them, until either the end of the pattern, or the next occurance of
+them, until either the end of the pattern, or the next occurrence of
C<\E>, whatever comes first. They perform similar functionality as the
functions C<lc> and C<uc> do.
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
If capturing parenthesis are used in a regular expression, we can refer
to the part of the source string that was matched, and match exactly the
-same thing. (Full details are discussed in L<perlrecapture>). There are
-three ways of refering to such I<backreference>: absolutely, relatively,
-and by name.
+same thing. There are three ways of referring to such I<backreference>:
+absolutely, relatively, and by name.
+
+=for later add link to perlrecapture
=head3 Absolute referencing
=head3 Relative referencing
-New in perl 5.10 is different way of refering 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
C<\g> always refers to a capture group and will never be seen as an octal
-escape). If the number is negative, the reference is relative, refering to
+escape). If the number is negative, the reference is relative, referring to
the Nth group before the C<\g{-N}>.
The big advantage of C<\g{-N}> is that it makes it much easier to write
=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>.
it will start the match from where it ended the previous time.
C<\G> matches the point where the previous match ended, or the beginning
-of the string if there was no previous match. See also L<perlremodifiers>.
+of the string if there was no previous match.
+
+=for later add link to perlremodifiers
Mnemonic: I<G>lobal.
=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>.
(vertical white space), and the multi character sequence C<"\x0D\x0A">
(carriage return followed by a line feed, aka the network newline, or
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,
+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
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