I doubt that list assignments can be implemented more efficiently w/o JIT magic.

The behaviour of caching all values before assigning them is well defined, e.g. in Learning Perl ch. 3.4:

Since the list is built up before the assignment starts, this makes it easy to swap two variables' values in Perl

OTOH one could have tied vars on LHS which are not side effect free, such that compatibility would break after optimization to a ring-replacement.

IMHO this can only be resolved at runtime .. (or with complicated precompiled case checks)