According to the perlbrew site, there is an option available for installing a cpanm instance that is shared across the different perlbrew perls. 
perlbrew install-cpanm

[download]
I think it will store it's configuration and data files (such as sources) in ~/.cpanm. I do not see similar support for cpan. I have not used this feature of perlbrew, so if I'm not correct, I hope someone will correct me.

In reply to Re^3: Proper CPAN Installation by kevbot
in thread Proper CPAN Installation by Cmdr Colstel

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