Thank you for your replies.
I attempted the solution using qx but I had the same result. Executing the command using the shell seems to be the problem, the sigalrm is not delivered. It's an interesting problem I haven't come across before.
I was considering using system to redirect the output of the command to a temporary text file and then reading the tmp file to parse output one line at a time.
I should also mention I am working on Win32 Boo! ;)