Getting up to speed on mod_perl with respect to writing Apache handlers is a non-trivial pursuit. While the rewards are often significant, you do need a pretty thorough understanding. I recommend the O'Reilly book, "Practical mod_perl." It's a fantastic resource, and will teach more than you ever thought you wanted to know about the subject.

If you don't want to get into it that deeply, use Apache::Registry. You still may get a strong performance boost over mod_cgi (plain old CGI), without having to know quite as much. It's one of those areas where you can't skip to the last chapter and hope to reap the benefits while at the same time producing bug-free code. But Apache::Registry gives you many of the benefits of mod_perl handlers, without quite as much of a learning curve. You still need to write pristine code, but you don't need to know as many details. The down side is slightly less performance, but that may be ok in your application.