#!/usr/local/bin/perl -w

use strict;

my $file = 'thesaurus';
open(INFO, $file);

print " What are you looking for?  ";
my $a = <STDIN>;
chop $a;

my @matches = grep { (index $_, $a) > -1 } <INFO>;

print "The following matches were found: @matches\n";
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Originally posted as a Categorized Answer.