Yeah, the grammar author does fully control the division between the parser and lexer: every literal (string or regex) in the grammar corresponds to a token. There's also a `token()` function that you can use to specify that an arbitrary rule should be handled by the lexer as a single token.

In most cases, you don't have to think about it; the obvious way to write something is the right way. There are cases where its helpful to have a mental model of how lexing works.