Sorry - I'm looking to have 6 groups, no fewer.

I'd like the groups scored by how many items they contain different from the ideal (the lower, the better):

my $ideal_avg_per_group = @list / 6;

# your solution
my $solution = [ 
 [1 1 1 2 3],
 [4 4 4 5 5],
 [6 6 6 7 7],
 [8 8 8]
];

my $this_score = 0;
for (@$solution) {
  my $num_items = @$_;
  $this_score += abs($ideal_avg_per_group - $num_items);
}
[download]

Also, it's fine to assume that there are more than 6 unique values in the list. Otherwise, it's obviously very easy.

Thanks!