The problem with doing this is that it bypasses perl's reference-counting memory management scheme. If you could ref-ify a stringified ref, you'd be getting a new reference to something without incrementing that thing's reference count. That means you could still have "live" references to an object which perl has already deallocated due to its reference count reaching zero.

Now that you know all that, if you really still want to reconstitute a reference from a string (and have no fear of the potentially nasty consequences) try the Devel::Pointer module.

See this post by Ovid for more information on references.