You could try:

#! perl -slw
use strict;
use Data::Dumper;
use DBI;

my $dbh = DBI->connect('dbi:WMI:');

my $sth = $dbh->prepare(<<WQL);
    SELECT * FROM Win32_SerialPort
WQL

$sth->execute();

while (my( $serial ) = $sth->fetchrow) {
    print Dumper $serial;
}
[download]

I can't confirm if it works, because I just discovered that this machine doesn't have any serial ports!

I guess if I ever need one, I'd have to buy a USB-serial adapter.