I've never used fork before, so I tried your code to see if I could learn something. I got the same errors as the rest of you, failing after 65 lines (printing 99 to 35).

But if I add either of the following before the child if statement

    if(!defined $pid){
      die "$runs: $!";
    }

OR
  
    if(!defined $pid){
      print FILE "undefined at $runs\n";
      $runs--;
      next;
    }
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it only prints 64 times (99 to 36). Actually, that's what I would expect.

Why do we get an error on the if ($pid == 0) { line, but then it still goes and prints one more time?

I also find it interesting that when I use my second if statement above, it prints down to 37, then all the undefined lines; and then it prints 36. Is there something significant about that?

TheEnigma