my $max = shift || 100;
my @nums = (2 .. $max);
my @primes;

while (@nums) {
    my $prime = shift @nums;
    push @primes, $prime;
    if ($prime ** 2 > $max) {
        push @primes, @nums;
        last;
    }
    @nums = grep {$_ % $prime != 0} @nums;
}

say "@primes";