I would say that you could look at the Slashcode project for an idea of how to do this. Slashboxes in the Slashcode environment are eval'ed in the manner you suggest.

I also like the approach suggested by the comment Re: Using eval to create 'plugins' from dws where he said that you could enforce testing on a development system by requiring a hash generated by Digest::MD5. You will never see an OpenSource project constructed this way, IMHO, because no project leader will want to require all implementations to have a separate staging environment. But, such a solution could work well in your case.