fibonacci in perl6 (for advent calendar)

fib.p6

use v6;

sub fibonacci (int $n --> int) {
    my int $x = 1;
    my int $y = 1;
    while $n > 0 {
        $x = $x + $y;
        $y = $x - $y;
        $n = $n - 1;
    }
    return $y;
}

for ^40 -> int $x {
    say fibonacci $x;
}