I recently got bogged down with using HTML::Template and persisting form fields when an error occurred in form processing. What I ended up doing was just using CGI.pm for creating the form fields. Each field can be set a default value by using the -default named parameter. So in this case, I just set the -default to $sess->{'whatever'}, and of course, if key 'whatever' doesn't exist, it just gets undef, no harm, no foul.

There are other options for prefilling your forms as well. Check out HTML::FillInForm.

The other thing you can do to simplify your scripts is use something like CGI::Application to organize your data. You can use the prerun/postrun hooks to create and persist your sessions automatically, so when you get down to actually programming logic, you don't have to think about those housekeeping things anymore.