you could try something like:

>script $HOME/cpan.log
Script started, file is cpan.log
>cpan install Net::FTP
.....
[download]

To stop logging type 'exit' at the command prompt, you should see something like <code>Script done, file is cpan.log. Perhaps there is a 'smarter' way to achieve this, but I think this should work for you.

Hope this helps

Martin