Anonymous recursive functions, getting error: warning: variable "fibonaci" does not exist

[NobbZ]

The best thing you can do, is to use 2 variables:

fib_ = fn
  0, f -> 0
  1, f -> 1
  n, f -> f.(n-1) + f.(n-2)
end

fib = fn(n) -> fib_(n, fib_) end

IO.puts fib.(10)

Please beware the autocorrection.