You seem to have misinterpreted the documentation for HTTP::Cookies. The add_cookie_header() method simply requires that your HTTP::Cookies object (called $cookie_jar in the examples) contains a cookie. The cookie is created using the set_cookie() method. There's also an extract_cookie() method for getting a cookie from an HTTP::Response object.

The save() and load() methods, for saving cookies to a file and loading them from a file, can be ignored if you don't want to save cookies to a file.