use strict;
use warnings;

use MCE::Loop;
use Data::Dumper;

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

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

MCE::Loop->init(
    chunk_size  => 1,
    max_workers => 4,
    init_relay  => 1,
);

my @result = mce_loop {
    my $token = $_;
    my $regex = build_regex($token);
    my @line_results = grep { $_ ne $token and /$regex/ } @tokens;
    MCE::relay {
        MCE->gather(\@line_results) if @line_results;
    };
} @tokens;

MCE::Loop->finish;

print Dumper(\@result), "\n";

__END__

$VAR1 = [
          [
            'bc'
          ],
          [
            'cd'
          ],
          [
            'de'
          ],
          [
            'ef'
          ],
          [
            'fg'
          ],
          [
            'gh'
          ]
        ];