Hi
You could check the first reply to this post on telnet error handling in your particular case.
Trapping errors in Net::Telnet::Cisco
As you might be aware Some routers dont allow users to logon using telnet for security reasons, and if they do for operational reasons, there might even be restictions on what type of commands can be used.
Having said that i see you were able to have some kind of a handshake with the router, so i guess its trial and error for you now.
All the best
The temporal difficulty with perl is u need to know C well to know the awesome.else u just keep *using* it and writing inefficient code