The use here is as a section, not to change precedence: `($ x)` could also have been written as `\f -> f x`, which I think is even less readable.

As for the usage on the lower code snippets like `for […] $ \x -> …`, then it saves some parentheses. Opinions on this go both ways, with some people preferring lisp-style syntax, others use more Python-like indentation code formatting. Both are okay, and I’ve switched my preference multiple times.

Where I agree $ is terrible is in expressions like `foo x . bar y z $ abc`, often (!) much harder to read than just adding parentheses.