$result = send( SOCKET, $synpacket, $num_of_bytes, $broadcastAddr );

perldoc -f send says

    send SOCKET,MSG,FLAGS,TO
    send SOCKET,MSG,FLAGS
[download]

so your invocation appears to be incorrect. Replacing $num_of_bytes with 0 gives me a successful outcome, although I did clean up your code a little before running so let us know if you still have problems.