One thing, not explicitly mentioned, that everybody should learn, i think, is seeing how a regex is matched and parsed via -Dr switch (perlrun(1)).

If/When you cover Schwartzian Transform (ST), consider covering a modified form of ST: Guttman-Rosler Transform. Around those two transforms, you could (re)introduce (un)pack functions.

After the coverage of references and around coverage of AUTOLOAD, symbol table manipulation, say for creating methods/subs, does not seem too much of a stretch.