Not sure about the Camel - I'm not sure there is a whole load of "don't cross the streams" stuff, although perhaps they do introduce some advanced stuff a little early.

I mean stuff like the autoincrement operator's magic on strings. If you're a new programmer, you can get along just fine without knowing that. Yet there it is, stuck right in chapter 3.

This is just to say that the Camel (and much of Perl's distribution docs) cover advanced stuff too early to be useful as a newbie guide. There are books that are good for that, though (like "Learning Perl").

if you didn't introduce arrays (I don't think PHP has them?

Hashes are just weird arrays with slow lookup times that allow you to dereference them with a string instead of a number. Of course, I'm hand-waving over a lot of implementation details here.