Update:

After some trial and error I discovered the root problem. I was trying to publish a distro whose name GHCN did not correspond to a module in the package; i.e. there was no GHCN.pm.

In hindsight the answer was in the PAUSE message.

Either someone else has ownership over that package name, or this is a brand new distribution and that package name was neither listed in the 'provides' field in the META file nor found inside the distribution's modules.

Obvious now, wasn't then. I was thinking of GHCN:: as a container for modules, but GHCN was not a sensible choice for the main entry point.

Once I figured that out, I decided that Fetch.pm would make a good entry point, and based on the other feedback I received here I decided to name the collection Weather::GHCN::Fetch.

Thanks again for your advice. It was most helpful.