Adding new things to global functions?

[unlimit]

local thelist = {};
thelist["am_i"] = true;
thelist["in_the"] = true;
thelist["list"] = true;
 
function IntheList(name)
    return thelist[name];
end

Let's say I have two addons. I would like to, from my addon, be able to add my words into "thelist", but it's a local variable. However, IntheList(name) is a global function, is there anyway override the global function from MY addon and make it return "thelist[name] AND theotherlist[name];"?, or manually (without editing the original addon) to add my words into thelist?

qts;dfr (question too stupid, didn't finish reading): Is there a way to make IntheList(name) return from anything OTHER than just thelist[name] without editing the original addon?