You didn't mention clearly, why do you install modules as a root. Is it a multi-user environment, or you are the only citizen in the system?

If you want installed modules to be seen by other users, the best place for them is /usr/local. And this should be the default setting on fresh run of CPAN -- unless in my case (Ubuntu 9.04). Either run 'o conf init' from inside CPAN shell, or remove ~/.cpan dir to start from the beginning.

If you want to install modules for yourself only, I'd recommend using local user's folder -- this is the way I work and had no problems with it yet. To do so:

1. Create folder ~/perl
2. set PERL5LIB=~/perl/lib/perl5 somewhere in startup script (e.g. ~/.bash_profile)
3. set following options in the CPAN

   o conf makepl_arg INSTALL_BASE=~/perl
   o conf mbuildpl_arg "--install_base ~/perl"
   [download]

(in above code ~ is your homedir, please expand it)

After that, the CPAN installation should place all files in ~/perl.