I suspect it’s because putting things into @_ requires making an alias to them, and you can do them for something that actually exists. print obviously works differently, being a builtin.

$ perl -w
my @a = ();
print $a[-1];
foo("$a[-1]");
sub foo { }
^D
Use of uninitialized value in print at - line 2.
Use of uninitialized value in string at - line 3.

I have no idea what should be done about this and how.

Makeshifts last the longest.