Sorry, that's rooted in my inadequate explanation. There are some infelicities, but not, TTBOMK, any bugs to find.
Rather, as a candidate for first script in a series, this one is aimed solely at familiarizing the user with the use of w(atch), l(ist) and company.
But you're absolutely correct that any such effort should include some simple scripts with obvious bugs and some more with more subtle problems... albeit, all in the class that is discoverable with straightforward use of the distribution's debugger. (I say "straightforward" because I'm quite sure some of our most skilled colleagues make the debugger jump thru hoops and do discovery-acrobatics well beyond the little I've learned.)