If you don't want to go the mod_perl route, mod_auth_mysql might be the ticket. It's pretty simple to setup and uses few resources. However, to use it in your situation you'll need to create a separate password field rather than derive a computed value from the username field. If you can't do this then creating an authentication handler in mod_perl is pretty simple.

mod_auth_mysql uses http authentication rather than cookie-based. I've used the module with good success for quite some time. Google turned up a good HOWTO for using it.