Someone gave name the answer over at:

StackOverflow User: mob

In general you must detach the child process from its parent to allow the parent to exit cleanly -- otherwise the parent can't assume that it won't need to handle more input/output.

} elsif ($pid == 0) {
   close STDIN;
   close STDERR;
   close STDOUT;   # or redirect
   do_long_running_task();
   exit;
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In your example, the child process is making print statements until it exits. Where do those prints go if the parent process has been killed and closed its I/O handles?