In your code you have use Net::Telnet but never use this module. Net::Telnet::Cisco is 12 years old. Before using any module you should read the open bugs, for this module there are 11 years worth, some claim that it can't connect to certain Cisco hardware. Perhaps you're experiencing the same problem. A Super search will reveal lots of nodes on the subject of automating Cisco interfaces with perl. Using Net::Telnet with the appropriate waitfors should be all you need.