In a setup with one frontend server that proxies to a
backend mod_perl server, authentication should be performed entirely
on one of the servers: don't mix and match frontend-
and backend-based authentication for the same URI.
File-based basic authentication (performed by mod_auth) is best done
on the frontend server. Only authentication implemented by mod_perl
handlers, such as Apache::AuthenDBI, should be
performed on the backend server. mod_proxy will proxy all
authentication headers back and forth, making the frontend Apache
server unaware of the authentication process.