use Win32::API;
my $GetLogicalDriveStrings = new Win32::API(kernel32 => GetLogicalDriveStrings => ['N', 'P'], 'N');
my $drives = "\0" x 4000;
my @drives;
if($GetLogicalDriveStrings->Call(length $drives, $drives)) {
    @drives = split /\0+/, $drives;
}