ikegami writes:

The launched perl doesn't have a child. Could you explain?

Yes, I misspoke, must have been temporarily missing all clue. Had been working on calling the shell from qx() and was lost in an incorrect mind set. Of course what ikegami is talking about is that perl is interpreting the users cat.pl script and not forking a child . Further discussion here has clarified ( somewhat ) that the problem lies in another direction.