> Maybe it's not implemented in PO 2013, but it can be read in the 2013 edition
> of the book Project Oberon (§ 3.3.1 on p. 30).
It is not implemented in PO 2013, but it is implemented in Extended Oberon, a variant of PO
2013 (although there it is called System.FreeImports) -- which is why I still remembered M*-