The ML and APL families also do function application without excessive parens. I don't think Lisp's grouping rules are complex. There are a few functions with

The ML and APL families also do function application without excessive parens. I don't think Lisp's grouping rules are complex. There are a few functions with special grouping, particularly let and cond, but anybody doing real programming in Lisp gets used to them pretty quickly. (Lisp is hardly the only language with special cases in its syntax!) User-added functions seldom have elaborate nesting schemes, or at least have a damned good reason.