When to escape magic characters

[Dirk Laurie <dirk.laurie@...>]

I thought one always needed to escape for example *.
I was wrong.

$ lua
Lua 5.3.1  Copyright (C) 1994-2015 Lua.org, PUC-Rio
> ("ab*c"):match"ab*"
ab
> ("ab*c"):match"ab?*"
ab*