Dave talks about the Python and leads into programming using an outliner. This is very interesting to me. I love Perl (the un-Python) and it is interesting that he talks about the advantages of programming using an outliner because this is what led me to contribute the outline-mode enhancements to emacs‘ cperl-mode.el.
Emacs is actually a pretty nifty folding editor. Here is how to use it to edit Perl code in this fashion.