Every time I explain something in the Modern Perl book under development, I have to change the way I think. I've spent a decade writing Perl 5, testing Perl 5, writing about Perl 5, editing writings about Perl 5, and thinking about how to do all of those. I still learn new things, but I haven't been a novice for a very long time.

Mature projects need the perspective of determined and intelligent novices to help find gaps in tutorials and documentation. It's too easy to assume that the mental model experienced users have is obvious for novices. After all, the design is clearly an effective design for the problems it has to solve.

The problem is two-fold. First, the novice may have very different problems and assumptions when approaching the software. Second, the expert mindset may be implicit: the result of experience developing the software, not approaching the problem fresh.

Any good documentation or tutorial intending to give novices practical experience must explain essential pieces of the model while avoiding too much explanation or gratuitious details. That's difficult to do in technical writing. (That's why most technical writing is passable at best and often atrocious.)

This is a long introduction to explain how I've spent a lot of time thinking about concepts that novices need to understand to take advantage of modern Perl. There are several:

Context: how it works, how to identify it, and how to take advantage of it. This includes both void/scalar/list context but also boolean/integer/string/numeric context.

Using perldoc: to review syntax and builtins as well as modules

Creating, managing, and using modules: including the packaging, testing, building, and deployment systems

Installing CPAN modules: especially with tools such as local::lib and, perhaps, a local CPAN mirror

Using the Perl 5 analysis tools: not limited to testing modules, Perl::Tidy, Perl::Critic, and B::Deparse

I thought about including "References and data structures", and I may do so. I left out OO on purpose. The same goes for most syntax; those are all learnable. This list tends toward the philosophical on purpose. These are necessary to understand Perl 5 and to take advantage of it (especially for further learning).

If a novice learns these five things, he or she is in good position to use Perl 5 effectively for almost any task. Leave out any one and you've added friction and frustration. Understand them and you can do almost anything in Perl 5.