To display the location, I changed the code accordingly and run 1 time. Running serially seems fast enough. Basically, Perl completes in less than 1 second for 1 million keys from an Intel i7 Haswell chip running at 2.6 GHz. Nethertheless, this post was written to demonstrate workers sending data to the manager-process for STDOUT via MCE->print(...).

Results: run 1 and 2 times for 1 million keys: $max set to 1e6.

$ perl demo2.pl haukex 1
Found at 999999
Found at 1000000
duration (haukex):  0.336 seconds

$ perl demo2.pl karlary 1
Found at 999999
Found at 1000000
duration (karlary): 0.231 seconds

$ perl demo2.pl karlseq 1
Found at 999999
Found at 1000000
duration (karlseq): 0.122 seconds
[download]

$ perl demo2.pl haukex 2
Found at 999999
Found at 1000000
Found at 999999
Found at 1000000
duration (haukex):  0.665 seconds

$ perl demo2.pl karlary 2
Found at 999999
Found at 1000000
Found at 999999
Found at 1000000
duration (karlary): 0.477 seconds

$ perl demo2.pl karlseq 2
Found at 999999
Found at 1000000
Found at 999999
Found at 1000000
duration (karlseq): 0.253 seconds
[download]

Below, workers report the location.

...

{
    no strict 'refs';
    my $start = time;

    $func->() for 1 .. $count;

    printf "duration ($func): %0.03f seconds\n", time - $start;
}

...

sub haukex {
    # serial code
    for my $key ( 1 .. $max ) {
        print "Found at $key\n" if (
            $barcode_hash{$key}[2] eq $barcode_pair_35
        );
    }
    return;
}

sub karlary {
    # workers receive next array chunk
    mce_loop {
        my ( $mce, $chunk_ref, $chunk_id ) = @_;
        for my $key ( @$chunk_ref ) {
            MCE->print("Found at $key\n") if (
                $barcode_hash{$key}[2] eq $barcode_pair_35
            );
        }
    }
    1 .. $max;  # <-- for array 1 .. $max
    return;
}

sub karlseq {
    # workers receive next sequence 'begin' and 'end' boundaries
    mce_loop_s {
        my ( $mce, $chunk_ref, $chunk_id ) = @_;
        for my $key ( $chunk_ref->[0] .. $chunk_ref->[1] ) {
            MCE->print("Found at $key\n") if (
                $barcode_hash{$key}[2] eq $barcode_pair_35
            );
        }
    }
    1, $max;    # <-- for sequence 1, $max
    return;
}
[download]