: Failed matches in Perl do not reset the match variables,
which makes it easier to write code that tests for a series of more
specific cases and remembers the best match.
@@ -583,6 +615,15 @@ already paid the price. As of 5.005, C<$&> is not so costly as the
other two.
X<$&> X<$`> X<$'>
+As a workaround for this problem, Perl 5.10.0 introduces C<${^PREMATCH}>,
+C<${^MATCH}> and C<${^POSTMATCH}>, which are equivalent to C<$`>, C<$&>
+and C<$'>, B that they are only guaranteed to be defined after a
+successful match that was executed with the C (preserve) modifier.
+The use of these variables incurs no global performance penalty, unlike
+their punctuation char equivalents, however at the trade-off that you
+have to tell perl when you want to use them.
+X X
+
Backslashed metacharacters in Perl are alphanumeric, such as C<\b>,
C<\w>, C<\n>. Unlike some other regular expression languages, there
are no backslashed symbols that aren't alphanumeric. So anything
@@ -636,17 +677,17 @@ whitespace formatting, a simple C<#> will suffice. Note that Perl closes
the comment as soon as it sees a C<)>, so there is no way to put a literal
C<)> in the comment.
-=item C<(?imsx-imsx)>
+=item C<(?pimsx-imsx)>
X<(?)>
One or more embedded pattern-match modifiers, to be turned on (or
turned off, if preceded by C<->) for the remainder of the pattern or
the remainder of the enclosing pattern group (if any). This is
particularly useful for dynamic patterns, such as those read in from a
-configuration file, read in as an argument, are specified in a table
-somewhere, etc. Consider the case that some of which want to be case
-sensitive and some do not. The case insensitive ones need to include
-merely C<(?i)> at the front of the pattern. For example:
+configuration file, taken from an argument, or specified in a table
+somewhere. Consider the case where some patterns want to be case
+sensitive and some do not: The case insensitive ones merely need to
+include C<(?i)> at the front of the pattern. For example:
$pattern = "foobar";
if ( /$pattern/i ) { }
@@ -660,9 +701,18 @@ These modifiers are restored at the end of the enclosing group. For example,
( (?i) blah ) \s+ \1
-will match a repeated (I!) word C in any
-case, assuming C modifier, and no C modifier outside this
-group.
+will match C in any case, some spaces, and an exact (I!)
+repetition of the previous word, assuming the C modifier, and no C
+modifier outside this group.
+
+These modifiers do not carry over into named subpatterns called in the
+enclosing group. In other words, a pattern such as C<((?i)(&NAME))> does not
+change the case-sensitivity of the "NAME" pattern.
+
+Note that the C modifier is special in that it can only be enabled,
+not disabled, and that its presence anywhere in a pattern has a global
+effect. Thus C<(?-p)> and C<(?-p:...)> are meaningless and will warn
+when executed under C