Just because I really like grinder's Regexp::Assemble, and think such a cool module needs more exposure:

#!/usr/bin/perl -w

use Regexp::Assemble;

my $lineFromSomeTextFile = "your line right here\n";
my $ra = Regexp::Assemble->new->add(
    "something",
    "matching",
    "a",
    "line"
);
print $ra->re . "\n"; # because the output is cool
                      # and sometimes educational
my($word) = $lineFromSomeTextFile =~ /($ra)/;

print "found '$word' in: $lineFromSomeTextFile";
[download]

(For more on Regexp::Assemble see: Why machine-generated solutions will never cease to amaze me.)

HTH,