Impressive! I could follow you step by step. After a second read (starting from the last step), I realized how the interpreter seems to work.
I think that I could simplify your work by excluding the "outer f" subroutine from the improved example, but as it is, is a great pedagogical example and explanation.
Thank you very much! And more thanks goes to ikegami.
BTW, this is not the way I program. I just wanted to understand what the OP was trying to explain. Everyday I learn something new of Perl's world. I'm not sure if I'm ready for Perl 6.