Lua high-level debugger

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

Am I describing your module, or close?

1. It provides interactive debugging.
2. It takes max 5 minutes of studying the README to get up to speed.
3. You run your Lua code with `lua -l mydebug` or the like.
4. At some point in the program where you need debugging, you put
    mydebug().
5. That routine calls a REPL which can list, inspect and change
variables visible at that point of the program and return.

Example:

!> x?
upvalue, table 0x34bc80, has __index chain (3 levels)
!> x.a?
in __index(1), number, -nan
!> x.a = 0
!> exit

This is not a sneaky advertisement for a module I already almost have.
I wish to know what is on the shelf already.