in reply to
CPAN won't work on Mountain Lion following attempt to install Bundle::CPAN
It's not clear to me what command you typed to get that error. But it's obvious the error is related to your system perl, which you should leave alone. Were you using the system perl's cpan command to install modules before this?
I don't think the system perl installs cpan modules. I think the whole idea is that Apple set up your computer by installing perl and configuring perl to allow Mountain Lion to do the things it needs to do. A customer wouldn't be very happy if Mountain Lion wouldn't work correctly without downloading addition modules from cpan. What if the customer didn't have an internet connection?