Didn't work, but one thing I noticed when doing this is that I have a `/usr/local/lib64/perl5` and a `/usr/local/share/perl5`, and there is (was) some overlap. One or the other was probably created by me as an option when running cpan for the first time, although I could not find a reference to it in the old ".cpan.bk".
So I merged the two and left a symlink, then tried tobyink's suggestion. Not sure which of those did the trick, but it now works.