Start Quantum again and reproduce what you see in the Quantum session below.

Use special functions Decf, Incf, Pop, Push, PushNew, and Setq to assign or change values to "places".  A "place" can be:

symbol   a Symbol
(Elt array i)   an element of a 1-dimensional Array
(Elt array [i_1 ...  i_n])   an element of an n-dimensional Array
(XXXXX struct)   a field of a Struct
[place_1 ...  place_n]   an Array of places

Assignment to an Array of places occurs in parallel (simultaneously, not sequentially).  You can use (Setq [x y] [y x]) to switch the values of Symbol's x and y , etc.

Use vanilla function SetSymbolValue to set a Symbol's global value.