#!/usr/bin/env perl

use v5.18;
use strict;
use warnings;
use autodie;
use MCE;

my @input_data  = (0 .. 100 - 1);

## Make an output iterator for gather. Output order is preserved.

sub output_iterator {
   my %tmp; my $order_id = 1;

   return sub {
      my ($result, $chunk_id) = @_;
      $tmp{$chunk_id} = $result;
      while (1) {
         last unless (exists $tmp{$order_id});

         open my $output, '>', "/path/to/my/files/$chunk_id.txt";
         foreach (1..10) { print $output "\t",fibonacci($_)};
         say $output;
         close $output;

         delete $tmp{$order_id++};
      }
   };
}

## Use $chunk_ref->[0] or $_ to retrieve the element.
my $mce = MCE->new(
   chunk_size => 1,     #setting to 1 = do not chunk
   max_workers => 8,    #number of CPU cores
   gather => output_iterator(), #the function which will be applied to each element of the array
   );

MCE->foreach( \@input_data, sub {
   my ($mce, $chunk_ref, $chunk_id) = @_;
   my $result = sqrt($chunk_ref->[0]);
   MCE->gather($result, $chunk_id);
});

sub fibonacci {
    my $n = shift;
    return undef if $n < 0;
    my $f;
    if ($n == 0) {
        $f = 0;
    } elsif ($n == 1) {
        $f = 1;
    } else {
        $f = fibonacci($n-1) + fibonacci($n-2);
    }
    return $f;
}