I may be missing something obvious, but there does not seem to be any consistent documentation in the current manual on the return values of metamethods. For example, nothing is said about the return value of the index metamethod when it is a function. In particular, what should happen if the function returns more than one value? I just had to debug some weird behaviour which was caused by such a metamethod, so I would be tempted to say it is wrong to return anything but one value, but that is not supported by official docs.
Cheers,
V.
