I had to help someone fix an issue with IPC:Open2 a week or so ago, we were seeing all the processes turn to zombies in a Linux environment.

Our problem was 2 fold, we were not flushing the buffers enough:

$| = 1;
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This fixed that problem (buffer by line instead of chunk).

The second problem was a little stranger (zombies invading our machines...late night sci-fi here we come!)

I had to read 3 docs on IPC:Open2 before I found this on the CPAN site (IPC:Open2):

open2() does not wait for and reap the child process after it exits. E
+xcept for short programs where it's acceptable to let the operating s
+ystem take care of this, you need to do this yourself. This is normal
+ly as simple as calling waitpid $pid, 0 when you're done with the pro
+cess. Failing to do this can result in an accumulation of defunct or 
+"zombie" processes. See perlfunc/waitpid for more information.
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You won't find this text (unfortunitly) in  perldoc perlipc. Or in the Camel, at least I can't find it :)

Hope this helps, and I'm not making some glaring error :)