In Julia you can go low-level, but there is no requirement. You can write purely high-level, generic, untyped code, with good performance. So I'm a bit reluctan

In Julia you can go low-level, but there is no requirement. You can write purely high-level, generic, untyped code, with good performance. So I'm a bit reluctant to accept the claim that it's lower level. What are the things where low-level code is required in Julia, but not in Python/R?