use strict;
use warnings;
use Benchmark qw(:all);

my @words;

my @letters = qw( A B C D a b c d );
build_words(\@letters, \@letters, \@letters, \@letters);
compare();

@letters = qw( d e f g h i k l );
build_words(\@letters, \@letters, \@letters, \@letters);
compare();

@letters = qw( B B B B b b b b );
build_words( [qw(A A A A a a a a)], \@letters, [qw(C C C C c c c c)], \@letters);
compare();

sub build_words {
        @words=();
        my ($rA, $rB, $rC, $rD) = @_;
        for my $a (@$rA) {
                for my $b (@$rB) {
                        for my $c (@$rC) {
                                for my $d (@$rD) {
                                        push @words, "$a$b$c$d\n";
                                }
                        }
                }
        }
}

sub compare {
        my $v = @words;
        my $t = regex();
        my $u = uccmp();
        if ($t != $u) {
                die "Functions don't return the same value! regex=$t, uccmp=$u\n";
        }
        print "In $v words, $t are 'abcb'\n";
        cmpthese(-5, {
                regex => sub { regex() },
                uccmp => sub { uccmp() },
        } );
}

sub regex {
        my $cnt=0;
        for (@words) {
                ++$cnt if /^abcb$/i;
        }
        return $cnt;
}

sub uccmp {
        my $cnt=0;
        for (@words) {
                chomp;
                ++$cnt if uc($_) eq 'ABCB';
        }
        return $cnt;
}