$system, used in your header way at the top is never defined at all, let alone before it is used.

You need to re-evaluate how you are doing things. It looks like you want to create a header down after you define @systems, then iterate over that through each one and use something like

"---$system[N]---\n".

Also,

use warnings;
[download]

...might have been useful, but I didn't test. Always use it.

-stevieb