You've already gotten an answer to the question you posed, so I'll add a minor coding suggestion.

You can eliminate a conditional by writing

  push @new_cookies, cookie_creator_sub() if <<some condition>>;
  ...
  $q->header(-cookie => [ @new_cookies ]);
[download]

If @new_cookies is empty, no cookies are added. This approach gives the flexibility of adding additonal cookies without having to modify existing code.