This isn't Lua, this is SmileBASIC. If you want to talk about Lua, then go to the Roblox forums.

C+ doesn't exist. And I'm pretty sure SmileBASIC is nothing like HTML and XML.

Roblox also isn't a programming game. It's a Lego clone that allows complex Lua scripting for the creation of games to be played by others. By your implication, Garry's Mod is a programming game. It is not.

hello world in Smilebasic is the same in lua

Just because Hello World is the same in both languages doesn't mean both languages are the same. There are a lot, and I mean A LOT of differences between the two.

and how do you know

Because I have coding experience in both languages.