Can´t access variables from file in function

[Azer0s]

c as word closed = 'Hello world'
fib:[1,1]
func fib[num a, num b]
	out:c
	asLongAs[true]
		out:a
		out:b

		a = $a + $b
		b = $a + $b

		case[$a bigger 10000]
		put a
		endCase
	endAsLongAs
endfunc

Throws an exception because of out:c