If you want a modern version of this, you should checkout https://github.com/RhodiumToad/pllua-ng

A friend of mine benchmarked different pl languages and https://github.com/eugwne/pllj was basically the fastest, but it's not so actively maintained. pllua-ng with luajit 2.1 was also faster than plv8. But that was about two years ago, your milage may vary.

"Lua is faster - PL/V8 is lightly faster than Python, but Lua is about 30% faster than PL/V8" - Pavel Stěhule and that was without luajit, but 4 years ago.

Maybe someone should build a benchmark :D