FunctionsFTW/Recursive Fibonacci

def("fib", (num "index") {
  if(eqNum(getNum("index"), 0), () {
    "F(0)";
    returnNum(0);
  }, () {
  if(eqNum(getNum("index"), 0), () {
    "F(1)";
    returnNum(1);
  }, () {
    "F(i-2) + F(i-1)";
    returnNum(add(callNum("fib", [ "index" add(getNum("index"), neg(2)) ]), callNum("fib", [ "index" add(getNum("index"), neg(1)) ])));
  }); });
});

setNum("x", 1);
label("l");
print(callNum("fib", [ "index" getNum("x") ]));
setNum("x", add(getNum("x"), 1));
goto("l");

Minimized (323 bytes)

def("f",(num "i"){if(eqNum(getNum("i"),0),(){returnNum(0);},(){if(eqNum(getNum("i"),0),(){returnNum(1);},(){returnNum(add(callNum("f",["i" add(getNum("i"),neg(2))]),callNum("f",["i" add(getNum("i"),neg(1))])));});});});setNum("x",1);label("l");print(callNum("f",["i" getNum("x")]));setNum("x",add(getNum("x"),1));goto("l");