use MCE::Loop max_workers => 4, chunk_size => 'auto';

   ## chunking takes 0m12s to complete (IPC becomes 11.5x faster)

   mce_loop {
      my ($mce, $chunk_ref, $chunk_id) = @_;

      my @o; for (@{ $chunk_ref }) {
         push @o, $_;
      }
      MCE->say(@o);

   } 1..4_000_000;