> the Lua 5.1 Reference Manual (hard copy) does not mention it [hex constants] You sure? It's right there on page 3, near the end of section 2.1, isn't it? It's also in the HTML version in the original 5.1 tarball. The wayback machine says it's there since the first version: http://web.archive.org/web/20060308051145/http://www.lua.org/manual/5.1/manual.html