This crashes:

function t()
  return
end

print(t())

I'm not sure how Lua describes this in language terms. The spec doesn't have much to say about returning no values; it's not a nil or table. (An empty list?) Lua 5.3.1 just prints an empty value.

This is Pico-8 0.1.3.

it's basically the same as running print() which crashes too =(
seems like a bug in pico8's print function.

Ah, yeah. :)

Thanks -- fixed for 0.1.4