my %count; $count{$_}++ for @temp;
my @non_unique_intersection = grep { $count{$_}-->0 } @temp2;

##</code><code>##

# 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;
}

##</code><code>##

my %count; $count{$_}++ for @temp;
my @non_unique_intersection = grep { $count{$_}-->0 } @temp2;
my (@leftovers, @leftovers2);
push @{$count{$_}>0 ? \@leftovers : \@leftovers2}, ($_) x abs($count{$_}) for keys %count;