sub find_unique_items_in {
        my $set = shift;
        
        my (%uniq, @out) = ();
        
        for $i (@$s) {
            $uniq{ $i }++;
        }
        
        push @out, sprintf (
            "%d unique entities (%d duplicates):\n", 
            scalar keys %uniq,
            scalar ( grep { $uniq{$_} > 1 } keys %uniq ),
        );
        
        for $i (sort keys %uniq) {
            push @out, sprintf ("%-16s -- %d", $i, $uniq{$i});
        }
        return (join ("\n", @out));
    }


    @list = (0) x 10;
    
    for (1..10) {
        $set = [];
        push @set_list, $set;
        
        for $i (0.. rand(5)+10) {
            push @$set, \$list[ rand @list ];
        }
    }
    
    for $s (@set_list) {
        print "\n", '-'x72 ,"\n\n";
        print join ("\n", @$s), "\n\n";
        print &find_unique_items_in ($s), "\n";
    }