This is a bit easier to handle than the pypi transition. The parts of the CPAN ecosystem are more disconnected. MetaCPAN/search.cpan.org (search and docs viewer), PAUSE (upload service), and CPAN (file mirrors) are all separate systems.
Didn't that transition not go very smoothly? I seem to remember having nowhere to download packages stuff at work when they turned the old system off (I think due to the new system not being able to handle the load, but I could be wrong)
There were issues with the CDN and redirects[0] for a couple of hours when they flicked the switch. Still, I think it was a very successful transition.