Works with lua 5.2 now (haven't tested 5.3 yet).

Originally it was written with luajit (with 5.2 compatibility on). But
the bit library is named differently than 5.2's bit32 library and is
slightly different.

Changed to work with whichever library is available.

bench.lua

@@ -1,7 +1,12 @@
 local mojibake =  require 'mojibake'
 
-local bit = require "bit"
-local tobit, tohex, bnot, band, bor, bxor, lshift, rshift, arshift, rol, ror, bswap=bit.tobit, bit.tohex, bit.bnot, bit.band, bit.bor, bit.bxor, bit.lshift, bit.rshift, bit.arshift, bit.rol, bit.ror, bit.bswap
+ --use "bit" library if available (luajit and external), "bit32" if not (lua 5.2)
+local bit_library_loaded,bit = pcall(require, "bit")
+if not bit_library_loaded then
+	bit = require "bit32"
+end
+local bnot, band, bor, bxor, lshift, rshift=bit.bnot, bit.band, bit.bor, bit.bxor, bit.lshift, bit.rshift
+
 
 function readfile(filename)
 	local f = io.open(filename, "rb");

mojibake.lua

@@ -39,8 +39,12 @@
  *  Implementation of libutf8proc.
  --]]
 
-local bit = require "bit"
-local tobit, tohex, bnot, band, bor, bxor, lshift, rshift, arshift, rol, ror, bswap=bit.tobit, bit.tohex, bit.bnot, bit.band, bit.bor, bit.bxor, bit.lshift, bit.rshift, bit.arshift, bit.rol, bit.ror, bit.bswap
+ --use "bit" library if available (luajit and external), "bit32" if not (lua 5.2)
+local bit_library_loaded,bit = pcall(require, "bit")
+if not bit_library_loaded then
+	bit = require "bit32"
+end
+local bnot, band, bor, bxor, lshift, rshift=bit.bnot, bit.band, bit.bor, bit.bxor, bit.lshift, bit.rshift
 local floor=math.floor
 
 local NULLTERM		=	1