You will get one SIGCHLD for any appearance of one or more kids. You have to reap kids until there are no kids to reap. Something like this:

      use POSIX qw(WNOHANG);

      while ((my $kid = waitpid(-1, WNOHANG)) > 0) {
        warn "$kid reaped\n" if $trace;
        delete $kids{$kid};
      }
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Ripped off from my column about stuff like that.

The best way is to simply do this polling at some opportune time in your main loop, since having it in a signal handler will break eventually.

-- Randal L. Schwartz, Perl hacker