The difference between a list and an array is often ignored...

Indeed; for never iterates over an array. for always iterates over a list.

What do either of those mean? Based on later replies, it seems like people are interpretting it in terms of whether or not $_ is an alias or a copy. But saying "$_ is an alias" or "$_ is a copy" actually means something clear.

Is there some other meaning? For example, when foreach is given an array, it might make a new list of aliases to each array member and then iterate over that list, and thus not ever directly iterating through the array. Now that I think of that, it fits what you wrote quite well, but doesn't match how others interpretted it. I guess this behavior matters if you modify the array (adding or removing members) while you are in the loop and I suspect that is what foreach does.

Is that all that you meant or are there other aspects?

imp, what did you mean?