Was working more on my slides when I ran into something a little curious with the implementation of guile.
(eqv? "5" "5")
Apparently in certain versions of guile this returns #f (2.0.9). However in later versions (2.0.13) this returns #t. It also returns #t in Racket. I'm not 100% sure what's going on (I think it has something to do with how strings are handled in the earlier versions, and how they do comparisons) but it was interesting to me to see that even in later implementations of the same Scheme interpreter there was disagreement over how certain bits were handled.
I'll likely hand-wave this as part of the presentation, but it was interesting nonetheless.