On $r = () = 4..5; vs @r = () = 4..5;
It's useful to look at this snippet to help understand what's happening:
$r = ($x, $y) = (1..10);
- Assignment is right associative.
- ($x,$y) = 1..10 sets $x, and $y and returns in scalar context returns the number of elements on the right hand side (in this case, 10). In a list context it will return a list of lvalues assigned to.
- So now we have reduced the above to $r = 10 which needs no explanation.
- Note that it doesn't matter what is in the middle term, as long as it puts the right hand assignment in list context.
If we look at @r = () = 1..10 we will see that the right hand assignment assigns to no lvalues and so returns an empty list. And thus @r is empty.