Referencing functions

I was wondering if its possible to pass a reference for a function, not for what that function returns and put that reference to another function, i mean, something like that:


function f1(av:int){
 trace(av);
}
var ob1:Object = new Object();
//ob1.f2 = function(){}
ob1.f2 = f1;
ob1.f2(3);//3 ok
function f3(){};
f3 = f1;
f3(2);//not ok

I mean, it works when the second function is inside an object, so how this can work when the second is not inside anything?