my $watchdog = "./watchdog.@{[time]}.$$";
  open WATCHDOG, ">$watchdog" or die "Cannot open $watchdog for output: $!\n";
  print WATCHDOG "This file may safely be deleted\n";
  close WATCHDOG;

  while( $universe->evolve ) {
    if( !(++$iters % 100_000) ) {
       last unless -f $watchdog;
    }
    # do some more stuff
  }

  do_logging();
  unlink $watchdog;