#!/usr/bin/perl

use strict;
use warnings 'all';

my %buckets;

my @set = "A" .. "D";

foreach my $run (1 .. 10_000) {
    my @values = @set;
    @values[$_,$a] = @values[$a=rand($_-1),$_] for (reverse 1..$#values);
    $buckets {"@values"} ++;
}

foreach my $key (sort keys %buckets) {
    printf "%4d: %s\n" => $buckets {$key}, $key;
}
printf "%d buckets\n" => scalar keys %buckets;
__END__
4955: B C D A
5045: D C A B
2 buckets