With respect, not sure if Net::Ping will work based on how I'm reading the OP. As I understand it, he wants to log into a device and then issue the ping *from* that device. In the Cisco world, we call this "proxy ping" and there is an SNMP way to do this as well - connect to a remote device via SNMP, issue a ping from it to somewhere, and then get the results in SNMP reponse.
Net::Ping would work if the ping was coming from the device where the script is running, but I think you'd need it locally installed on the remote machine or better, just use system or backticks to execute ping from the remotely connected to machine to the target.
Of course, I could be misunderstanding the OP - without code or more detail, I'm just guessing as well.