Once again, hi :)

Using a simplified demonstration, regular expression appears to be 3x slower in Perl v5.20 and higher. I'm not sure why.

use strict;
use warnings;

use MCE;

sub task {
    my ( $mce, $slurp_ref, $chunk_id ) = @_;

    # open file handle to scalar ref
    open my $input_fh, "<", $slurp_ref;

    while (<$input_fh>) {
        if (/^sample\s+(\S+)/) {
            ;
        }
        elsif (/^good\s+(\S+)/) {
            ;
        }
    }

    close $input_fh;
}

MCE->new(
    chunk_size => '1m', max_workers => 4, use_slurpio => 1,
    user_func  => \&task
);

MCE->process({ input_data => "test.txt" });
MCE->shutdown;
[download]

Results

$ time /opt/perl-5.8.9/bin/perl -I. test_demo.pl

real    0m3.826s
user    0m14.352s
sys     0m0.133s

$ time /opt/perl-5.10.1/bin/perl -I. test_demo.pl

real    0m4.369s
user    0m16.935s
sys     0m0.126s

$ time /opt/perl-5.12.5/bin/perl -I. test_demo.pl

real    0m4.889s
user    0m18.944s
sys     0m0.134s

$ time /opt/perl-5.14.4/bin/perl -I. test_demo.pl

real    0m4.860s
user    0m18.865s
sys     0m0.127s

$ time /opt/perl-5.16.3/bin/perl -I. test_demo.pl

real    0m4.815s
user    0m18.724s
sys     0m0.129s

$ time /opt/perl-5.18.4/bin/perl -I. test_demo.pl

real    0m4.668s
user    0m18.356s
sys     0m0.116s

$ time /opt/perl-5.20.3/bin/perl -I. test_demo.pl

real    0m14.195s
user    0m49.155s
sys     0m7.282s

$ time /opt/perl-5.22.4/bin/perl -I. test_demo.pl

real    0m14.316s
user    0m49.586s
sys     0m7.041s

$ time /opt/perl-5.24.3/bin/perl -I. test_demo.pl

real    0m14.612s
user    0m50.251s
sys     0m7.531s

$ time /opt/perl-5.26.1/bin/perl -I. test_demo.pl

real    0m14.212s
user    0m49.418s
sys     0m6.999s

$ time /opt/perl-5.28.0/bin/perl -I. test_demo.pl

real    0m14.308s
user    0m49.476s
sys     0m7.137s
[download]

Regards, Mario