RosettaCodeData/Task/Anonymous-recursion/Arturo/anonymous-recursion.arturo

fib: function [x][
    ; Using scoped function fibI inside fib
    fibI: function [n][
        (n<2)? -> n -> add fibI n-2 fibI n-1
    ]
    if x < 0 -> panic "Invalid argument"
    return fibI x
]

loop 0..4 'x [
    print fib x
]