use strict;
use warnings;

my ($max, $p, @prime, $limit) = (100, 2, 2);
PRIME:
while (1) {
    $limit = int sqrt(++$p);
    for (@prime) {
        last if $_ > $limit;
        next PRIME if $p % $_ == 0;
    }
    push @prime, $p;
    last if $max == $#prime + 1;
}