my $sum = 0;
for my $pattern (map unpack('b4', pack 's', $_), 0 .. 15) {
    my $prod = 1;
    for my $i (0 .. 3) {
        $prod *= (\@A, \@B)[substr $pattern, $i, 1][$i];
    }
    $sum += $prod;
}
say $sum;