80% of the CGI interaction out there is "single form, single response" apps. I think your statement doesn't apply there. There's nothing wrong with putting the HTML and the response handler in the same file for that.

And if you do that, you gain the sticky-fields features of CGI.pm's form creation, and some high level constructs for radio-groups and checkbox-groups.

I think you're throwing the baby out with the bathwater when you say "don't use CGI.pm's HTML constructs". For 80% of the apps out there, it's just fine. I can agree with you that it doesn't scale, though. And when someone gets to one of those other 20% of the apps, they'll learn Template Toolkit or something.