We generally only tolerate this low quality of writing in journalism. Technical books of any sort are, and should be, held to a higher standard.
You are always right. But it depends on how it is classified when it is sold. It shouldn't depend solely on the authors opinion, don't you think? That is where critics should do their job.
I mean, Larry Wall once stated a difference between programing well and becoming a qualified expert. It all depends on what you use perl for.
I like naive aproaches to perl programing, because their target is very limited. Then certain readers do not feel intimidated by complex academic concepts. Perl is a better tool than DOS's Batch, but people is still using that limited language! Or even other more esoteric ones. Some simpler languages succeed in fields where perl should always be the main reference. Just because their authors were not pretending more than what they targeted to.
I wonder what would had happened if Windows people had always worked with perl as a glue language to do simple things. Perhaps, they would have all been now working with LINUX :) .