Problem:

• If you employ none of them:

  It is almost impossible to write a program -- that despite compiling clean -- functions correctly.

• If you employ all of them;

  It is almost impossible to write a program that actually compiles -- even if it would function perfectly correctly.

So the challenge as a newbie is what level of prophylactic should you employ?

And as a reasonably experienced Perler; what level should you employ to ensure that your perfectly functional code cannot be trivial modified in an incorrect way without tripping a warning or error of some kind; without having burdened it with overhead such that it is entirely useless?

And, IMO, the answer is: you cannot. In the end, one has to assume some more-than-beginner, less-than-expert level of competence from those that will follow you.

Attempting to pander to the lowest common denominator, is an exercise in futility; and more damaging to the language than obfuscation!