I thought the documentation of Apache::RegistryFilter described the usage of the filter as a filter chain. A wild guess is that you probably need to swap the order of your PerlHandler line, so that the registry filter appears at the end of the chain -
according to the Apache::Filter documentation, the filters are listed in forward order, so putting Apache::LC first lowercases the perl script, and then hands it to RegistryFilter to execute, which isn't what i want at all (and produces blank output when i try it).