Re^2: creating a regular expression's alternation dynamically?

In the join, you might want to map quotemeta over @list so that any meta-chars (particulary |) get escaped.

Also you have to be careful that none of the strings are prefixes of another string, otherwise you'll find that ordering is significant in an alternation.

--
integral, resident of freenode's #perl

Comment on Re^2: creating a regular expression's alternation dynamically? Download Code

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Re^3: creating a regular expression's alternation dynamically? by mifflin (Curate) on Aug 06, 2004 at 17:27 UTC
yep, good point, thanks! `use strict; use warnings; # create alternation my @list; while (<DATA>) { chomp; push @list, $_; } my $regex = '^(' . join('\|', map {quotemeta} @list) . ')$'; my $s = 'huey'; print "regex = $regex\n"; print "match:\t$1\n" if $s =~ m/$regex/; __DATA__ huey de\|wey louie` [download] output is... `# perl test.pl regex = ^(huey\|de\\|wey\|louie)$ match: huey` [download]	[reply] [d/l] [select]

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Re^3: creating a regular expression's alternation dynamically?
by mifflin (Curate) on Aug 06, 2004 at 17:27 UTC

use strict;
use warnings;
#   create alternation
my @list;
while (<DATA>) {
    chomp;
    push @list, $_;
}
my $regex = '^(' . join('|', map {quotemeta} @list) . ')$';
my $s = 'huey';
print "regex = $regex\n";
print "match:\t$1\n" if $s =~ m/$regex/;
__DATA__
huey
de|wey
louie
[download]

# perl test.pl
regex = ^(huey|de\|wey|louie)$
match:  huey
[download]

[reply]
[d/l]
[select]