perl6ish fibonacci

fib.pl

# vi: ft=perl6
use v6;

sub fib(Int $x) {
    constant @fib_list = 0, 1, * + * ... *;
    die "non-negative arguments required"
        unless $x >= 0;
    @fib_list[$x];
}

sub MAIN(Int $fib) {
    say fib($fib)
}

thanks to @colomon for the obvious solution with the sequence