Do you honestly think in terms of lists when you do $a[4]? I don't.
Neither do I. But that's not the point. The issue is, what do you think when you see
@a[4]? The sigil makes me think "list". It turns out to be a one element list. Good. Nothing wrong with that. IMO.
But Perl warns. It thinks there might be a problem.
I can't figure out what you think I was saying, but hopefully this clears it up.
I cannot figure out whether you think that it's good that Perl warns about
@a[1] or that you think it shouldn't warn, but it gives the programmer the freedom to signal the intent to use a list.