Maybe is possible to do what you want, but if you only want a local repository, you can save yourself a lot of trouble using CPAN::Mini.

I've being using it in a regular PC without Internet connection with good results. Of course you will need to configure the CPAN module to use your local repository.

I have faced some issues regarding the CPAN shell not being smart enough to grab the files 01mailrc.txt.gz, 02packages.details.txt.gz and 03modlist.data.gz by itself (it keeps trying to fetch them from the Internet) but this can be easily solved if you just gunzip them before running reload index in the CPAN shell.