I'm not sure I follow. If someone heads to a login page, there's no form yet. On their way, they're redirected over a secure link. When they get to the login page, they're on HTTPS. They enter secret information, it goes over HTTPS, and if they're appropriately authenticated, they get sent to some other page over HTTP, and there's no secret information being sent any more.
It's the same for my other examples--a user tries to visit http://www.mysite.com/edit/secret_table?id=12, they get switched to a secure link before they get there, not after they're entered info.
Back to mod_perl for a sec--does this have to be handled in a PerlTransHandler, or can I just remap the URL in the regular handler I'm using?