Am I the only one that has read this book and become confused by the use of modules in a solution 3 chapters before they are introduced for the 1st time???

I think that the explicit purpose is to make you work out the code without using any module. Granted, it happens all the time that when we see a newbie doing so we recommend using the suitable modules instead. But it is a task that can be done reliably (at least on a fixed system) enough with regexen and other basic tools, so in the context of an exercise it may well make sense...

I don't know the book, but I wouldn't be surprised if at a later point it would say: "do you remember when we had you doing so and so? Well, now forget about that and use File::Basename".