Jonathan got an honors degree from Cambridge University in CS specializing in compilers etc. If you pay attention to his slides you'll see he's paid to train others to use a variety of languages (all kinda boring ones, except P6 imo, but still). Imo you are underestimating his expertise and the import of what he's saying in his presentation.

The bit that I'm still confused about is how the interleaving of run-time inside compile-time inside run-time inside compile-time etc. contributes to the imposition of compile-time type checking via run-time code and how far that paradigm can go. I'd appreciate you (or anyone else) carefully explaining that bit to me. :)

  $ perl -Mstrict -M"feature 'say'" -c morning.pl 
  Global symbol "$moroning" requires explicit package name at morning.pl line 7.
  morning.pl had compilation errors.

Such a typo catcher would be a written (I'm thinking of a lisp or lua here) on the editor side, having the information about the variable and being able to query the namespace or locals visible or not visible. The things jonathan did was just to put this into the compiler for the thrills, but it can be easily extracted, extended and customized from the outside, in emacs, vi, eclipse, ... such as jonathan did with his perl6 debugger.