Thanks for your help! I tried to implement most of your improvements and I think I've got them working now - but I've still got that weird problem with the array. When it divides by all the numbers in the array, it doesnt always start from 2 (the first element). If you look at the output it seems that in the end it does divide by all of them, but doesn't start with the first element. In doing so it works some bits out twice. For example if you set the limit to 13 then it will divide 11 by 2,3,5 and 7. Now it should realize that it 11 is prime and add it into the array. But when it then starts working on 12, it starts of by dividing by 11 instead of 2. I thought the push function added the value on to the end of the array? Well it doesn't really matter, but I guess it makes the program quite a bit slower, especially with larger numbers. Thanks in advance, Martin

print "Set a limit\n";
$limit = <STDIN>;
chomp $limit;
@primes = (2);
$zahl = 2;
$isprime = 1;





for (my $number = 3; $number < $limit; $number++) 

    {
        @primes = sort @primes;
        $isprime = 1;
                
                foreach $divisor (@primes)
            {
                print "Dividing $number by $divisor\n";
                    if ($number % $divisor == 0) 
                    {
                        #print "$number is no Primenumber\n";
                        @primes = sort @primes;
                        $isprime = 0;
                        last;
                    }
            
            }

    if ($isprime == 1) 
        {
        #print "$number is a primenumber\n";
        @primes = sort @primes;
        push (@primes, $number);
        }
    }
[download]