I did a dump like you said and it was very helpful.  I needed to add the code below to make it work

Turns out that I need a unique key for every disk that I am adding.  Thank you for your help

my $disk = VirtualDisk->new(

       controllerKey  => $devSpec->device->controllerKey,

       unitNumber     => $devSpec->device->unitNumber,

       key            => -1 *($i + 1),

       backing        => $devSpec->device->backing,

       capacityInKB   => $devSpec->device->capacityInKB,

    );

$devSpec = VirtualDeviceConfigSpec->new(

    operation     => $devSpec->operation,

    fileOperation => $devSpec->fileOperation,

    device        => $disk,

);

Is there a better way to do it than this