use Win32::SerialPort;
my $port = Win32::SerialPort->new("COM8")
  or die "New port failed. $!\n";

$port->baudrate(9600); # you may change this value
$port->databits(8); # but not this and the two following
$port->parity("none");
$port->stopbits(1);

#$port->rts_active(1); # has no (useful) effect
#$port->dtr_active(1); # has no (useful) effect

...