user_func   => sub {
         my ( $mce, $slurp_ref, $chunk_id, $output ) = ( @_, '' );
       # open my $fh, '<', $slurp_ref;
       # while ( <$fh> ) {
       #    chomp;
       #    my $n = 0;
       #    $n += $_ - $n % $_ * 2 for @rtoa[ unpack 'c*', $_ ];
       #    $output .= "$n\n";
       # }
       # close $fh;
         # output orderly
         MCE::relay {
       #    print $output;
         };
      }