=head1 NAME
-perlfaq6 - Regexes ($Revision: 1.3 $, $Date: 2001/10/16 13:27:22 $)
+perlfaq6 - Regular Expressions ($Revision: 1.10 $, $Date: 2002/04/07 18:32:57 $)
=head1 DESCRIPTION
decoding a URL and checking whether something is a number are handled
with regular expressions, but those answers are found elsewhere in
this document (in L<perlfaq9>: ``How do I decode or create those %-encodings
-on the web'' and L<perfaq4>: ``How do I determine whether a scalar is
+on the web'' and L<perlfaq4>: ``How do I determine whether a scalar is
a number/whole/integer/float'', to be precise).
=head2 How can I hope to use regular expressions without creating illegible and unmaintainable code?
sub preserve_case {
my ($from, $to) = @_;
my ($lf, $lt) = map length, @_;
-
+
if ($lt < $lf) { $from = substr $from, 0, $lt }
else { $from .= substr $to, $lf }
-
+
return uc $to | ($from ^ uc $from);
}
An elaborate subroutine (for 7-bit ASCII only) to pull out balanced
and possibly nested single chars, like C<`> and C<'>, C<{> and C<}>,
or C<(> and C<)> can be found in
-http://www.perl.com/CPAN/authors/id/TOMC/scripts/pull_quotes.gz .
+http://www.cpan.org/authors/id/TOMC/scripts/pull_quotes.gz .
The C::Scan module from CPAN also contains such subs for internal use,
but they are undocumented.
=head2 What's wrong with using grep or map in a void context?
-Both grep and map build a return list, regardless of their context.
-This means you're making Perl go to the trouble of building up a
-return list that you then just ignore. That's no way to treat a
-programming language, you insensitive scoundrel!
+The problem is that both grep and map build a return list,
+regardless of the context. This means you're making Perl go
+to the trouble of building a list that you then just throw away.
+If the list is large, you waste both time and space. If your
+intent is to iterate over the list then use a for loop for this
+purpose.
=head2 How can I match strings with multibyte characters?
-This is hard, and there's no good way. Perl does not directly support
-wide characters. It pretends that a byte and a character are
-synonymous. The following set of approaches was offered by Jeffrey
-Friedl, whose article in issue #5 of The Perl Journal talks about this
-very matter.
+Starting from Perl 5.6 Perl has had some level of multibyte character
+support. Perl 5.8 or later is recommended. Supported multibyte
+character repertoires include Unicode, and legacy encodings
+through the Encode module. See L<perluniintro>, L<perlunicode>,
+and L<Encode>.
+
+If you are stuck with older Perls, you can do Unicode with the
+C<Unicode::String> module, and character conversions using the
+C<Unicode::Map8> and C<Unicode::Map> modules. If you are using
+Japanese encodings, you might try using the jperl 5.005_03.
+
+Finally, the following set of approaches was offered by Jeffrey
+Friedl, whose article in issue #5 of The Perl Journal talks about
+this very matter.
Let's suppose you have some weird Martian encoding where pairs of
ASCII uppercase letters encode single Martian letters (i.e. the two
=head1 AUTHOR AND COPYRIGHT
-Copyright (c) 1997-1999 Tom Christiansen and Nathan Torkington.
+Copyright (c) 1997-2002 Tom Christiansen and Nathan Torkington.
All rights reserved.
This documentation is free; you can redistribute it and/or modify it