out of the docs:

Net::Ping->new([$proto [, $def_timeout [, $bytes]]]);

Create a new ping object. All of the parameters are optional.
$proto specifies the protocol to use when doing a ping.
The current choices are ``tcp'', ``udp'' or ``icmp''.
The default is ``udp''.
[download]

Do u use the right proto ?

Have a nice day
All decision is left to your taste
Update
ack, I get old and slower