Sorry, hit send too fast.
No, the code in question is testing whether the argument (filename) is
_exactly equal to_ "-", not whether it _contains_ '-'.
Maybe. But I want to hear the Lua Team.
This is not a maybe, your change does not do the same thing and is wrong, you don't need the Lua team to tell you that, you can read the man pages of these functions or believe what everyone here is telling you.