Another option is to install modules into application specific libraries.

I have systems running multiple perl applications, each with its own module requirements. While the modules installed on the system are usually adequate, sometimes newer or older or patched versions are required for a particular application. To avoid adversely impacting the system or other applications, I prefer to install such modules into an application specific library - just a few more modules among the application's own modules.

I am currently investigating options for cpan and cpanplus to have them use application specific configurations rather than the system wide or personal configurations. I don't see easy support for this out-of-the-box, so I expect I will customize cpanplus to make installation and maintenance of these modules easier.