I'm a little confused ... did you actaully *want* a local mirror of the stuff you're installing, or did you just want to make you life easier when picking your CPAN mirror during CPAN.pm configuration?
If the later, then you don't seem to have made life any easier, since your mirror can only deal with one URL (for reasons that aren't clear). Picking one URL when configuring CPAN isn't really that hard.
You probably could have achieved the same thing (without needing any local disk, actaully using multiple mirrors) by configuring your DNS server to make "cpan-mirror.yourdomain.com" round robin through the mirrors you want to use.