use PDL;

sub is_a_set {
  all (($_[0] + $_[1] + $_[2]) % 3) == 0;
}

sub third_card {
  (pdl(3,3,3,3)-$_[0]-$_[1]) % 3;
}

my $X = pdl(0,1,2,2);
my $Y = pdl(0,2,2,1);
my $Z = pdl(0,0,2,0);

if (is_a_set($X, $Y, $Z)) {
  print "$X, $Y and $Z form a set\n";
} else {
  print "$X, $Y and $Z do not form a set\n";
}

print "To form a set with $X and $Y you need: ", third_card($X, $Y), "\n";