It looks as if any complex sub-expressions /subroutine calls are evaluated in order, and
variables/references are evaluated last.
That's very astute of you. It's not exactly what's going on, but it's very close.
For simple variables, Perl pushes what is
effectively a reference onto the stack.
But for complex ecpressions, Perl must construct the
new value and push a reference to that instead. So if
$i = 2
, then $i
in the list pushes a
reference to $i
itself, but $i + 0
and pushes a reference to the copy of the 2. If you later change
, the first 2 changes but the second one doesn't.
Your original example works the same way.
This could be considered a bug. It has come up on p5p before,
but I don't remember what the outcome of the discussion was.
Contrary to what chromatic said, it is not a precedence issue.
Precedence only affects parsing, not execution.