use strict;
use warnings;

use Parallel::ForkManager;
use MCE::Shared;
use Data::Dumper;

my @tokens = qw( ab bc cd de ef fg gh );

sub build_regex {
    my ($token) = @_;
    chop $token;
}

my $pm = Parallel::ForkManager->new(4);
$pm->set_waitpid_blocking_sleep(0);

tie my %result, 'MCE::Shared';

DATA_LOOP:
foreach my $token ( @tokens ) {
    # forks and returns the pid for the child
    my $pid = $pm->start and next DATA_LOOP;

    my $regex = build_regex($token);
    my @line_results = grep { $_ ne $token and /$regex/ } @tokens;
    $result{ $token } = \@line_results if @line_results;

    $pm->finish(0);
}

$pm->wait_all_children;

print Dumper( tied(%result)->export({ unbless => 1 }) ), "\n";

__END__

$VAR1 = {
          'ef' => [
                    'fg'
                  ],
          'fg' => [
                    'gh'
                  ],
          'cd' => [
                    'de'
                  ],
          'de' => [
                    'ef'
                  ],
          'bc' => [
                    'cd'
                  ],
          'ab' => [
                    'bc'
                  ]
        };