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| author | Andrew M. Langmead <aml@world.std.com> | 1997-09-05 00:00:00 +0000 |
|---|---|---|
| committer | Tim Bunce <Tim.Bunce@ig.co.uk> | 1997-09-05 00:00:00 +1200 |
| commit | 201ecf35b0c6aa83b4332b0a53bdf68f2a7b8840 (patch) | |
| tree | 7b9d24dcafa28fb37d6ff86fd660304583ad841f /pod | |
| parent | 1c98b8f6f310a0c48429445cfa3c296d19df5faf (diff) | |
| download | perl-201ecf35b0c6aa83b4332b0a53bdf68f2a7b8840.tar.gz | |
The description of the \Q metacharacter is confusing to novices
The perlre man page talks about "quoting" metacharacters. This may
not be the easiest terminology for novice perl programmers to
understand. Also this man page seems to downplay the utility
of the quotemeta() function and \Q escape sequence compared
to the older idiom of s/(\W)/\\$1/g
Maybe text similar to the changes below would be clearer.
p5p-msgid: 199708101946.AA06339@world.std.com
Diffstat (limited to 'pod')
| -rw-r--r-- | pod/perlre.pod | 21 |
1 files changed, 11 insertions, 10 deletions
diff --git a/pod/perlre.pod b/pod/perlre.pod index 37434a67e7..14892a8846 100644 --- a/pod/perlre.pod +++ b/pod/perlre.pod @@ -136,7 +136,7 @@ also work: \L lowercase till \E (think vi) \U uppercase till \E (think vi) \E end case modification (think vi) - \Q quote regexp metacharacters till \E + \Q quote (disable) regexp metacharacters till \E If C<use locale> is in effect, the case map used by C<\l>, C<\L>, C<\u> and <\U> is taken from the current locale. See L<perllocale>. @@ -226,19 +226,20 @@ you've used them once, use them at will, because you've already paid the price. You will note that all 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 that looks like \\, \(, \), \E<lt>, \E<gt>, \{, or \} is always -interpreted as a literal character, not a metacharacter. This makes it -simple to quote a string that you want to use for a pattern but that -you are afraid might contain metacharacters. Quote simply all the +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 that looks like \\, \(, \), \E<lt>, \E<gt>, +\{, or \} is always interpreted as a literal character, not a +metacharacter. This was once used in a common idiom to disable or +quote the special meanings of regular expression metacharacters in a +string that you want to use for a pattern. Simply quote all the non-alphanumeric characters: $pattern =~ s/(\W)/\\$1/g; -You can also use the builtin quotemeta() function to do this. -An even easier way to quote metacharacters right in the match operator -is to say +Now it is much more common to see either the quotemeta() function or +the \Q escape sequence used to disable the metacharacters special +meanings like this: /$unquoted\Q$quoted\E$unquoted/ |