As I wrote, one reason is that I my code is modeled on a fragment from autobox's docs. But then as I also wrote, this is just one possible situation in which a similar case of (what I call) "double hardcoding" may happen. More seriously, the additional class is indeed a worker class, and is just there to keep things separated and clean: in a more realistic example, Array::Extract may have its own subs and methods, and I rightly want to define separately the methods that will work on autoboxed objects.