The way I have gone about this is getting the package that's provoking the update to 5.6.1 (which may be IO::Socket, as I recall) and do a manual upgrade - then rerun CPAN - that should do the trick.

Getting the latest CPAN is sound advice as it stops the former braindead "reinstall perl Yay!" default, but it won't fetch the "last known good" depended upon package for you...

Cheers,
alf