You cant do this with Net::Telnet::Cisco the way it sounds like you are wanting it to act...You may have to go into somthing like this using just Socket...Somthing like this:

#!/usr/bin/perl
use Socket;
# no its a quicky, i didnt use strict..its hard to write
# code in this text box

$HOSTNAME = "hostname.of.router";
$TELNETTO = "where.to.telnet.to.from.hostname";

$USER = "username";
$PASS = "password";

while (1) {
     socket(SOCK,PF_INET,SOCK_STREAM,getprotobyname('tcp'));
     connect(SOCK, sockaddr_in(23,inet_aton("$HOSTNAME")));
     select(SOCK);
     $|=1;
     select('stdout');
     print SOCK "$USER\n";
     while(<SOCK>) {
          ($stuff) = split(/\s+$/,$_);
           if ($stuff =~ /Password:/) {
                 print SOCK "$PASS\n";
           }

           if ($stuff =~ /\>$/) {
                 # we have user access
                 print SOCK "telnet $TELNETTO";
                 # do some matching on its prompt
           }
     }
     exit;
}
[download]

hope this helps a bit...its kinda what I had to do to get extended ping sweeps to work before.