Online lua compiler : https://rextester.com/l/lua_online_compiler
lua index :
strings hfst 20 : https://www.lua.org/pil/20.html
lua basis : https://riptutorial.com/nl/lua/example/11420/ermee-beginnen
lus strings : https://docs.coronalabs.com/guide/data/luaString/index.html
frontier pattern : https://stackoverflow.com/questions/32852605/how-to-check-if-a-word-appears-as-a-whole-word-in-a-string-in-lua