Thanks for your answer!

I think HTML::Mason looks great but, like you said, the use outside of mod_perl seems kludgy.
Apache::ASP uses the same trick. You call a Perl script called "asp" which emulates the mod_perl environment.
The latest EmbedPerl won't work with CGI, but they are working on it.
So far Apache::ASP looks most promising. I had a few errors running through the examples in the distribution, but most of them worked.