#!/usr/bin/env perl
# https://www.perlmonks.org/?node_id=11147200

use strict;
use warnings;
use MCE;

die "usage: $0 infile1.txt [ infile2.txt ... ]\n" unless @ARGV;

my $OUT_FH; # output file-handle used by workers

# Spawn worker pool.
my $mce = MCE->new(
    max_workers => MCE::Util::get_ncpu(),
    chunk_size  => '64K',
    init_relay  => 0, # specifying init_relay loads MCE::Relay
    use_slurpio => 1, # enable slurpio
    user_begin  => sub {
        # worker begin routine per each file to be processed
        my ($outfile) = @{ MCE->user_args() };
        open $OUT_FH, '>>', $outfile;
    },
    user_end => sub {
        # worker end routine per each file to be processed
        close $OUT_FH if defined $OUT_FH;
    },
    user_func => sub {
        # worker chunk routine
        my ($mce, $chunk_ref, $chunk_id) = @_;
        process_chunk($chunk_ref);
    }
)->spawn;