Get DBD::WMI and try this:

#! perl -slw
use strict;
use DBI;

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

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

$sth->execute();
while( my @row = $sth->fetchrow ) {
    printf "DeviceID: %s Description: %s \n", @row;
}

__END__
C:\test>SerialPorts.pl
DeviceID: COM3 Description: BCM V.92 56K Voicemodem
DeviceID: COM1 Description: Communications Port
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