you have omitted the fact that dereferencing an anonymous function
Quite intentionally. I didn't want to distract from the topic: dereferencing "data structure references". I wanted people to be able to let that sink in and then never worry about it again. Perhaps a title change is in order, though I don't want a title that will scare people off either. (:
Had I chosen to cover code references, then I would have been more detailed than what you've discussed above. I started to and then realized I didn't have handy the details required to cover that topic in a manner deserving of the label "tutorial" (and also realized that it didn't fit in anyway).
I also didn't talk about creating references, symbolic references, blessed references, closures, ref, UNIVERSAL::isa(), references to globs, to the IO chunks of globs, to compiled regular expressions, nor to any other types of things that Perl lets you have a reference to.
All of those break some of the above rules and discussing them would distract the reader from once and for all getting those rules down. I also lump data structure references together in my head while thinking of code references separately from glob references separately from...
So, no, I'm not going to add your two things to my list. q-:- tye (but my friends call me "Tye")