I agree with your concern that there's not a central location where this is explained.

In the interests of starting a partial list:

Perl Glossary: Autovivification

Perl Ref: Using References

Perl Ref Tut (buried in an example)

Exists function (example)

Open and related functions that use file handles

That's about it!

So it certainly warrants its own section, covering the pitfalls, and referencing other Perl documentation elements that relate to it.