I've done quite a bit of Scheme in the past, but I've been playing with Common Lisp a little recently, and I often find myself thinking things like "how do I convert a string to a list of characters" or "how do I check if this thing is in this list", like simple standard library stuff that I could implement myself but expect to already be there, and then I go look in the Hyperspec, and sometimes it's hard to find thing when you don't have a name to look up.