#!/usr/bin/env perl -l

use strict;
use warnings;
use autodie;

use List::Util qw{first};
use Tie::File;

my @strings = qw{rst uvw xyz};
my $re = '(?:' . join('|', @strings) . ')';

tie my @lines, 'Tie::File', 'pm_1155868_input.txt';
my $match = first { /$re/ } @lines;
untie @lines;

print "Match: '$match'";

##</code><code>##

$ cat pm_1155868_input.txt
aaaaaaaaaaaaaa
bbbbbbbbbbbbbb
cccccccccccccc
dddddddxyzdddd
eeeeeeeuvweeee
fffffffrstffff
gggggggggggggg
hhhhhhhhhhhhhh
iiiiiiiiiiiiii

##</code><code>##

Match: 'dddddddxyzdddd'