IMHO It's less about what is wrong with Log4perl and more about what is wrong with releasing a CPAN module that depends on Log4perl. If WWW::Mechanize::Chrome had been built on Log::Any, this unit test would be able to plug it into (my) Log::Any::Adapter::TAP and have the log messages be an official part of the TAP stream. Meanwhile people using WWW::Mechanize::Chrome in production could plug it into Log4perl if they want really fancy logging and everyone goes home happy.

Personally I never use Log4perl because I subscribe to daemontools philosophy that all logging of a service should stream through stderr and a separate dedicated logger process should read that pipe and handle all the advanced logic to sort/filter log messages. I like the separation of concerns better than trying to put advanced logging configuration into each perl service.