Problem with append function

[BruceH]

Trying to do some simple things with lists in a program but not getting very far.

Code:

EXPORT test()
BEGIN
  LOCAL xx := {};
  LOCAL yy := 3;
  append(xx, yy);
  RETURN(xx); 
END;

I'd expect that to return { 3 } but actually you get {}. Have I missed something obvious?
(Emulator version 2015 6 17 Rev 8151)

(Edit) And in Home I get some equally strange results:

Code:

append({},3)      {3}
L1                 {}
append(L1,3)      {3}
L1                 {}