Good advice

advice is emacs' way of letting you modify the behavoir of functions by wrapping them with before/after/around handlers. I don't usually have much use for it because there are better ways to customize things like properly asking the user for configuration ((if users-configuration (funcall users-configuration)))), and I'm also not a big fan of globally changing behavior. I did finally find one case

[antipop]

adviceでperlのパスを変更。これ、選べるようにしたいなぁ。5.10使うようになったらやるかー。