What you have proven is that it's possible to declare a lexical at file-scope that works a lot like a package global (but not exactly), but without generating an entry in the package global symbol table. Thus, this file-scoped lexical is not available outside the package (ie, via some fully qualified name, nor outside the enclosing file).

That doesn't show anyone how to cause an object's instance data to be available prior to object creation time, to a package bound sub (or a class method), which seems to be the question.