Many programming-language modes assume by default have traditionally assumed that any opening delimiter parenthesis or brace found at the left margin is the start of a top-level definition, or defun. Therefore, @strong{don't put an opening delimiter at the left margin unless it should have that significance}. For instance, never put an open-parenthesis at the left margin in a Lisp file unless it is So, by default, commands which seek the start beginning of a top-level list. defun accept such a delimiter as signifying that position.