#!/bin/perl

use strict;
use warnings;
use sigtrap;
use diagnostics;

my $mac="ff:ff:ff:ff:ff:ff";
my $command = system (`tshark -i eth0 -n port 68 -R 'bootp.type == 2' -o column.format:'"Source MAC","%hs"'`);
if ($command ne $mac) {

        system ('echo "match" | /usr/bin/mail -s "mac_found" user@foo.com');
}