...
# w/o ALT1,2 - try: $SIG{__DIE__} = sub { warn "\nDIIIII\n", caller };
    $fw = new Net::Telnet::Netscreen( host => $host );

# ALT1: Ignore (bad idea, but quick debugging fix):
#       $fw->errmode("return");
# ALT2: Analyse problem yourself / decide to abort or to continue:
#       $fw->errmode( sub { warn "ERRHANDLER: @_\n"; } );
...