use Win32::DriveInfo;

use constant {
    SECTORS_PER_CLUSTER => 0,
    BYTES_PER_SECTOR    => 1,
    FREE_CLUSTERS       => 2,
    TOTAL_CLUSTERS      => 3,
    BYTES_FREE_4_CALLER => 4,
    TOTAL_BYTES         => 5,
    TOTAL_FREE          => 6,
};

#$sql = "\\\\server01\\d\$";
$sql = "c:";

print "$sql\n";
print "Drive	Free	Tot	PctFree\n";

my @info = Win32::DriveInfo::DriveSpace($sql) 
    or die "DriveSpace failed with error: $^E";

printf "%.3f GB free of total %.3f GB\n", 
     $info[ TOTAL_FREE ] / 1024**3, 
     $info[ TOTAL_BYTES ] / 1024**3;

##</code><code>##

c:\Perl>drivelist.pl
\\server01\d$
Drive   Free    Tot     PctFree
0.000 GB free of total 0.000 GB

c:\Perl>drivelist.pl
c:
Drive   Free    Tot     PctFree
31.639 GB free of total 74.444 GB