# my @non_unique_intersection = nonunique_intersect( \@temp, \@temp2 );

sub nonunique_intersect {
  my ($x, $y) = @_;
  my %count; $count{$_}++ for @$x;
  my @return = grep { $count{$_}-->0 } @$y;
  return wantarray ? @return : \@return;
}