use MCE::Loop chunk_size => 1, max_workers => 8;

   my @input = (100..199);

   open my $fh_1, '>', '/path/to/file1.txt';
   open my $fh_2, '>', '/path/to/file2.txt';

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

      if ($chunk_id % 2 == 0) {
         MCE->say($fh_1, "id: $chunk_id: input $_");
      } else {
         MCE->say($fh_2, "id: $chunk_id: input $_");
      }

   } @input;

   close $fh_1;
   close $fh_2;