The typical use would be for each form to be a separate application (in the CGI::Application sense) and for every possible action (show the form, process the input) to be a separate run mode. Not having to do things like check wether or not the submit button was clicked is the whole point of CGI::Application.

Note that you can have one run mode call another. For example, if the user calls the "submit" run mode, but some data is missing, you can call the "display" run mode, passing along some extra data about the input error.