open (my $DEVICE, "<", 'device.list') or die "Could not open device list:$!";
while (<$DEVICE>) {
  chomp;
  my $routerIP = $_;
  print "Router IP is $routerIP,";
  my $session = Net::Telnet::Cisco->new(Host => "$routerIP", Input_log=>"input.log", 
               );
 if (! $session){
   warn "Could not open session to $routerIP\n";
   next;
 }
 if (! $session->login("$username", "$password") ){
      warn "Could not login to $routerIP\n";
   next;
 }
 my @output = $session->cmd("$cmd");

....  process ...
}