An eval provides its own 'scope', so anything lexical you do is limited to that scope.

But even if it weren't, it wouldn't do you much good. The biggest effect 'my' has is at compile time - it tells the compiler you have a lexical variable. However, the eval happens at run time - if you'd use '$a' after the eval, '$a' is unknown at compile time (so, if 'use strict' is in effect, it will complain).