Simpler yet!

use strict;
use warnings;

my $modules = shift;
my $second_group = int($modules/2);
printf "Call %d on port 80, %d on port 8080\n",
    $modules - $second_group, $second_group;
[download]

Yeah, brain circuits were irrevocably committed to using ceil() in there somewhere, to no real point in a simple case like this.