#!/usr/bin/perl -w
use strict;
use warnings;

use IO::Handle;

my ($Interface, $Multicast, $Port) = ('eth3', '226.1.109.109', '12345');

open (TCPDump,"sudo /usr/sbin/tcpdump -i $Interface host $Multicast 2>/dev/null |") || die "Can't open tcpdump : $!";
TCPDump->autoflush(1);

while (<TCPDump>) {
 print "$_";
}