This has done a zillion times before, so I guess you posted it for critique.

Some comments, in random order:

• use strict.
  • Declare variables.
  • Quote strings.
• use warnings.
• Don't use Dutch variable names.
• Use steps of 2, not one.
• Every prime number (except for 2 and 3) is 6x - 1 or 6x + 1.
• The inner loops needs only to check up to the square root.
• As calculating primes gets much slower as the numbers are larger, consider printing them immedately instead of storing them first.
• Indent.
• Don't have empty else blocks.
• Don't comment closing brackets. If what they close is unclear, something of your style is wrong and needs to be fixed.
• Think about your style anyway. I find it hard to read. Whitespace and lining up can do wonders.

To prove the last point, here's your code, with only stylistic changes made and the addition of strict compliancy. (Note: untested code!)

#!/usr/bin/perl -w

use strict;

system 'clear';

print "I will calculate the primes from 1 to the number you enter. Wha
+t is the maximum number to check?\n";

my $max = <STDIN>;
$max > 0 or die "Negatives or 0 not allowed!\n";

my $getal = $max + 1;

for (; $getal--; $getal >= 0) {
    my $deeltal = 2;  # A/B would give B in this case
    my $teller  = 0;  # A/B would give A in this case

    while ($getal % $deeltal != 0 and $deeltal + 2 <= $getal) {
        $teller++;
        $deeltal++;
    }

    if ($teller + 3 == $getal) {
       push @priemlijst, $getal;
    }
}

system 'clear';

push @priemlijst, 2;  # Don't forget number 2!

@priemlijst = reverse @priemlijst;

print "The primes from 1 to $max are: @priemlijst\n";
[download]

#!/usr/bin/perl -w
use strict;

$| = 1;

chomp(my $max = <STDIN>);

print "\n2 ";

N: for my $i (3 .. $max - 1) {
    for my $k (2 .. $i - 1) {
        next N if $i % $k == 0;
    }
    print $i, " ";
}

print "\n";
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#!/usr/bin/perl -w
use strict;

$| = 1;

chomp(my $max = <STDIN>);

print "\n2 ";

N: for (my $i = 3; $i < $max; $i += 2) {

    next unless $i % 6 == 5 or $i % 6 == 1;

    for (my $k = 3; $k < sqrt $i; $k += 2) {
        next N if $i % $k == 0;
    }

    print $i, " ";
}

print "\n";
[download]

Thanks for your reply, I appreciate it. I just coded it to practice my perl skills, it was not so much about the 'content' itself. The Dutch variable names: I wanted to show the code to my teacher so I commented in Dutch. I translated it to English to put it online, but I forgot to transform the variable names, so sorry for that. I was indeed a bit lazy when I was coding cause I never really thought about using tabs and whitelines cause I knew it would be a very small piece of code, but I know it's not an excuse hehe :) Anyway thanks for the hints, hope to hear from you later cheers azerton

See Prime Iterator for some interesting code on finding primes. Let me know if you don't understand how the code works.

thanks for the link and the compliment. Just felt like sharing it with you guys.

C:\>primes 4 50
5
7
11
13
17
19
23
29
31
37
41
43
47
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Abigail-II's C.L.P.M. Post