I was hoping for some magic trick using perl syntax, like aliasing the lexical function in a 'for' loop while localizing it, or maybe something involving an attribute that would trigger MODIFY_CODE_ATTRIBUTES and then use experimental ref assignment to overwrite the CV that the ref is pointing to, or something.

If PadWalker was core that would be one thing, but an XS module would be even further out of the question for avoiding dependencies.