This test:

if ($result >> 0)
[download]

should be

if( ( $result >> 8 ) != 0 ) {
[download]

Or more simply:

if( $result >> 8 ) {
[download]

If that doesn't fix your problem, then you will need to print out the failure code (print $result >> 8) and then look that up in the documentation for the executable to determine what the errorcode means.