#!/usr/bin/perl -w

use strict;

system 'clear';

print "I will calculate the primes from 1 to the number you enter. What 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";