The scripting language for Halo 1/2/3/ODST/Reach were based on Lisp. Halo 4 kept a similar syntax but got rid of the parentheses to be more BASIC-like. Halo 5 and now Infinite moved on completely to Lua.

Halo 1 reference: https://andrew.gg/scripts/00reference.html

Decompiled campaign scripts: https://github.com/Nibre/blamscript/blob/master/blamscript/h...