Soul,
Check whether you have established the connection with the remote server by checking the return value of each the  $telnet -> ... commands.
Also, in your code, you have used single quotes as in  print $telnet->cmd( 'dir' );, but in your problem statement, you mention backticks "`".

You might also want to have a look at this node.
Perform a Super Search, where you might get more useful hints.

Cheers,
Rupesh.