Sorry, I'm late to the party, but just for the record: Log4perl isn't resetting $@ here, it's a 3rd party appender from CPAN called Log::Dispatch::FileRotate. (You can easily verify this by replacing it by Log4perl's native file appender Log::Log4perl::Appender::File).

Might be a good idea to file a bug against it in order to have it localize its use of $@, although, as others have pointed out, it's a common mistake.