However, I find the coverage of object orientation in the last two chapters plain dreadful. The point of OO is abstraction, separation of different aspects of a problem in order to get reusable components of limited complexity. A textbook should aim to showcase how a carefully designed component is indeed reusable.

Johnson misses this mark rather spectacularly when he builds a "Queue" class based on a "Stack" class that has of course to be changed in the course of this endeavour (and thus proven not to be reusable).

I recommend students to switch to Learning Perl Objects, References and Modules after chapter 17. Besides that, I like the book.