In the Flash viewer, you cannot use the pop() method to populate a previously undeclared variable or property, whereas in the HTML5 viewer you can. Consider the following code:
Code
set(test1, "hello world!");
push(test1);
pop(test2);
trace(get(test2));
set(test1, "hello again!");
push(test1);
set(test3,);
pop(test3);
trace(get(test3));
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In the Flash viewer, test2 remains null. Only if the variable is first declared (even as a null variable) the pop method actually populates the variable. In the HTML 5 viewer, both tests work.
http://files.fieldofview.com/temp/krpano/stack
I'm not sure if this is a bug, but at least it is an inconsistency between the Flash viewer and the HTML5 viewer. In any case I am leaving this here in case someone's trying to find out why popping a variable isn't working the way it is in the HTML5 viewer.