Stolen, cannibalized and slightly adopted from this older thread: Threads From Hell #2: How To Search A Very Huge File [SOLVED]:

#!/usr/bin/env perl

# http://www.perlmonks.org/?node_id=1202693
#     $Id: loop.pl,v 1.2 2017/11/04 11:02:41 karl Exp karl $

use strict;
use warnings;
use MCE::Loop;
use Time::HiRes qw( time );
use feature qw(say);

my $file = q(data.txt);

MCE::Loop::init( { max_workers => 4, use_slurpio => 1 } );

my $start = time;

my @result = mce_loop_f {
    my $slurp_ref = $_[1];
    my @column;
    open my $fh, '<', $slurp_ref;
    binmode $fh, ':raw';
    while (<$fh>) { push @column, substr( $_, 10, 1 ) }
    close $fh;
    MCE->gather(@column);
    # sleep 2;
}
$file;

say join( '', @result );

printf "Took %.3f seconds\n", time - $start;

__END__
[download]

Thanks to marioroy.

See also MCE.

Update: To avoid the call to binmode please see Encoding horridness revisited: What's going on here? [SOLVED].

Regards, Karl