my $owner_is_still_running = `@$_`;             # search for a specific $pid
if ( $owner_is_still_running ) {
  print "$owner_is_still_running, keeping $1";  # found $pid, keep tempfile
} else {
  print "removing $1";                          # didn't find $pid
  `rm $1`;                                      # remove $pid's tempfile
}