in reply to HTTP-Server-Simple-0.44 tests and undefined $self->host

This is weird. In theory, HTTP::Server::Simple would call ->lookup_localhost, which should fix $host.

There are two bug reports that sound somewhat similar to your problem, but at least one claims that changes similar to yours solved the problem. The tests in H:S:S assume that localhost will resolve (to a local address) - maybe on your machine, this is not the case? This would be very weird, but I'd still check.