You're right, CLU is actually where Lua took them from. From "The Evolution of Lua"
> From CLU we took multiple assignment and multiple returns from function calls. We regarded multiple returns as a simpler alternative to reference parameters used in Pascal and Modula and to in-out parameters used in Ada; we also wanted to avoid explicit pointers (used in C).
> From CLU we took multiple assignment and multiple returns from function calls. We regarded multiple returns as a simpler alternative to reference parameters used in Pascal and Modula and to in-out parameters used in Ada; we also wanted to avoid explicit pointers (used in C).