A few days back I wrote a prime generator just because I hadn't done it in a while. I thought it came out pretty nice. It caches the primes that it finds and uses them for finding the new ones (that is, it uses the algorithm discussed by other monks: checking each candidate against primes less than the candidate's square root). Here it is:
use strict;
use warnings;
my @primes = ( 2, 3 );
my $candidate = $primes[1] + 2;
my $max_prime = shift  100_000;
CANDIDATE:
while ( $candidate < $max_prime ) {
my $sqrt_candidate = sqrt $candidate;
PRIME:
foreach my $prime ( @primes ) {
last PRIME if $prime > $sqrt_candidate;
next CANDIDATE if 0 == $candidate % $prime;
}
push @primes, $candidate;
}
continue {
$candidate += 2;
}
print join q{,}, @primes;
print "\n";

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