As others have said, use top to see if you're running out of memory. That seems the most likely culprit.

If the amount of output from your programs is large, an improvement that would reduce memory usage would be to change the child code to:

        unless ($cpid[$i]) { 
            exec 'perl',$_
              or die "exec error: $!\n";
        }
[download]

(You might have to play around with file descriptors a little to make this work just right). Using backticks causes another fork to be done, with the resulting parent reading the child's output, storing it into a scalar variable, then when the child exits prints the results. Using exec instead saves a fork, and instead of reading all of the input into a scalar variable, just lets the child write to stdout directly.

Also, adding better error checking, along with use strict and the -w flag might help you locate errors that are making your program behave in unexpected ways.

How many programs are listed in @gets?