It's possible that the derived class uses the parent class in the older version and that the authors decided to change that. Let's do some historical research on the module.

I don't find anything in the CHANGES file about that, but I just did a few quick string searches for what seemed obvious to me and didn't read the whole thing. Your searches might turn something up from that source if you look.

Here it is though: version 0.70_08 of SOAP::Transport::TCP does include a use SOAP::Lite; statement. I'm not sure which version was the last to do that, but now we have confirmed that at least one previous version did. If it was necessary, the svn repository or the web interface to it would make it fairly easy to find out when the change occurred.