The curious error message is the result of a known issue with Scalar::Util described here.

Update: I would try force install Scalar::Util (from the cpan shell) — maybe the Perl update for whatever reason installed the non-XS version...

Update 2: ...sorry, forgot that it's your cpan shell which isn't working :)  so you'll probably want to install the module the manual way, i.e. perl Makefile.PL && make install

Update 3: (last update, promised!)   Maybe it has to do with this bug...