But now, whenever I go to configure and bring my CPAN up to date, it is attempting to install 5.8.0. I'm fairly certain that I am doing something foolish here.

No, it's not you. Older versions of CPAN did that. Newer versions don't any more.

What I last did was, from within the CPAN shell, is try to update CPAN in the manner it suggests. As soon as it tries to build Perl 5.8.0, I interrupt it by pressing ctrl-C (twice?). Despite the interruption, CPAN now is updated. So it shouldn't try this stupid trick any more. You can notice because now you have a command line history buffer at your disposal.

Actually, I don't see what you are doing differently than me.