How do I build Perl regular expressions dynamically?

Question

I have a Perl script that traverses a directory hierarchy using File::Next::files. It will only return to the script files that end in \".avi\", \".flv\", \".mp3\", \".mp4\", a

Answer 1

Build it like you would a normal string and then use interpolation at the end to turn it into a compiled regex. Also be careful, you are not escaping . or putting it in a character class, so it means any character (rather than a literal period).

#!/usr/bin/perl

use strict;
use warnings;

my (@ext, $dir, $dirp);
while () {
    next unless my ($key, $val) = /^ \s* (ext|dirp|dir) \s* = \s* (\S+)$/x;
    push @ext, $val if $key eq 'ext';
    $dir = $val     if $key eq 'dir';
    $dirp = $val    if $key eq 'dirp';
}

my $re = join "|", @ext;
$re = qr/[.]($re)$/;

print "$re\n";

while (<>) {
    print /$re/ ? "matched" : "didn't match", "\n";
}

__DATA__
ext = avi
ext = flv
ext = mp3
dir = .svn
dirp= .frames