Hrmm, looks like it's returned by SOAP::Transport::HTTP::Server by calling a coderef (look for $response_content_writer in SOAP::Transport::HTTP::Apache) which is passed to its handle_request method (which prints to an Apache instance obtained with Apache->request()). All of the class names are hardcoded so there's not really a clean way to subclass. What you're going to have to do is basically make your own version of S::T::H::Apache and modify the coderef to do the error mucking.