in reply to Cross-developing in 5.005 and 5.6 (code)
But that detail aside, you will find your answer in the documentation for eval. Which is where you should have looked first.
OTOH when you are done that you will find yourself reaching for answers to several other questions. For instance why is strict not being picked up? Also why is 5.005 going to fail to pick most of those modules?
A far, far better solution is to create useless fallback versions of 5.6 specific modules. Then just use away with no trickery.