sub open_COM {
   ...
   $tie_ob = tie(*PORT,'Win32::SerialPort', $cfgfile); #Create filehandle only local
   ...
   #DEBUG
   print PORT "42, why not?\n"; # Yepp, working
   ...
}

sub txd {

   my $msg = shift;
   printf PORT "%s\n\r",$msg; # ouch... NOT working
   usleep(200000);
}