sub verify {
    for my $letters (1, 4, 26) {
        my $input = join '', map { ('a'..'z')[rand($letters)] } 0..20000-1;
        my @RobertCraven = RobertCraven($input);
        my @hdb = hdb($input);
        my @kennethk = kennethk($input);
        my @xxx = xxx($input);
        die "Mismatch 1 ($letters)" if @RobertCraven != @hdb;
        die "Mismatch 2 ($letters)" if @RobertCraven != @kennethk;
        die "Mismatch 3 ($letters)" if @RobertCraven != @xxx;
        for my $i (0 .. $#RobertCraven) {
            die "Char mismatch 1($letters, $i)" if $RobertCraven[$i] ne $hdb[$i];
            die "Char mismatch 2($letters, $i)" if $RobertCraven[$i] ne $kennethk[$i];
            die "Char mismatch 3($letters, $i)" if $RobertCraven[$i] ne $xxx[$i];
        }
    }
}