autovivification is completely unrelated to the aliasing process you asked about. Aliasing is the correct and magical term for what happens to Perl loop variables (but not their C equivalents) and to what happens with @_ elements which are aliases of the parameters passed into a sub.

This is very important and subtle magic and the word "alias" captures exactly what is going on. A large part of the magic is that most of the time you don't need to be aware of it.