my $state = 128; # start state, binary: 1000 0000
my $lightmask = 16; # 0001 0000
my $bellmask  =  8; # 0000 1000

sub togglelight {
   $state = $state ^ $lightmask;
   $port->write("<f 1108 $state");
   $port->lookclear();
}

sub bellon {
   if (not ($state & $bellmask)) {
      $state = $state ^ $bellmask;
      $port->write("<f 1108 $state");
      $port->lookclear();
   }
}

sub belloff {
   if ($state & $bellmask) {
      $state = $state ^ $bellmask;
      $port->write("<f 1108 $state");
      $port->lookclear();
   }
}