File-like string scanning

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

I find myself writing my own code for functions string.lines(...) and
string.read(...) so that str:lines and str:read have the same semantics
as file:lines and file:read, except that they are use-once since strings
can't store position.

I can't believe that I'm the first person who has though of doing this.
Any pointer to a module that does it nicely will be appreciated.