use Algorithm::Combinatorics qw(subsets);
use List::Util qw(sum);

my @data = (5, -6, 8, 10, 12, 3, 10);
my $iter = subsets(\@data);
while (my $subset = $item->next) {
  if (sum(@$subset) == 21) { print "found a solution: @$subset\n" }
}