You can also let Net::Ping do it for you...

# Like tcp protocol, but with many hosts
$p = Net::Ping->new("syn");
$p->port_number(getservbyname("http", "tcp"));
foreach $host (@host_array) {
   $p->ping($host);
}
while (($host,$rtt,$ip) = $p->ack) {
    print "HOST: $host [$ip] ACKed in $rtt seconds.\n";
}
[download]

Cheers,
R.