#!/usr/bin/perl -w

use strict;


my @lines = (
              'this is line one',
              'this is line TWO',
              'this is line three',
              'this is line four perl',
              'this is line fiveperl',
              'perl'
              );

my @search = grep { index($_,'perl')+1 } @lines;
# my @search = grep {/perl/} @lines;
#
# if you don't want line five use /\bperl\b/;

print "TRUE\n" if (@search);

foreach (@search) {
    print "$_\n";
}

##</code><code>##

Benchmark: timing 100000 iterations of index, re...
     index:  4 wallclock secs ( 3.54 usr +  0.00 sys =  3.54 CPU) @ 28248.59/s (n=100000)
        re:  7 wallclock secs ( 6.98 usr +  0.00 sys =  6.98 CPU) @ 14326.65/s (n=100000)