You can use Win32API to determine if the drive is writable by using the following code. The operation that you send to "DeviceIoControl" is "IOCTL_DISK_IS_WRITABLE" however there is no information about it so I had to go back to the C++ docs.

use strict;
use warnings;

use Win32API::File 0.08 qw( :ALL );

my $sRootPath = "d:/";
if(GetDriveType( $sRootPath ) == 5){ # then this is a CD-ROM
    my $sPath = "//./D:";
    my $uAccess = 0;
    my $uShare = FILE_SHARE_READ();
    my $pSecAttr = [];
    my $uCreate = OPEN_ALWAYS();
    my $uFlags = 0;
    my $hModel = 0; 
    
    my $hDisk= CreateFile( $sPath, $uAccess, $uShare, $pSecAttr, $uCre
+ate, $uFlags, $hModel) or  die "Can't read attributes of $sPath: $^E\
+n";
    
    my $controlcode = IOCTL_DISK_IS_WRITABLE;
    my $inbuff = [];
    my $inbuffsz = 0 ;
    my $outbuff = [];
    my $outbuffsz = 0;
    my @bytesret = [];
    my $overlap = [];
    if (DeviceIoControl($hDisk,$controlcode,$inbuff,$inbuffsz,$outbuff
+,$outbuffsz,@bytesret,$overlap)){
        print "Status = device is write enabled\n";
    }else{
        print "Status = $^E\n";
    }
}
[download]

I have tested this against a floppy with read/write and read only access set and it works correctly, however since I don't have a RW CDRom I can't test it further.