I've been using
Code:
local realmlist = GetCVar("realmList")
local region = string.match(realmlist,"(%a+)%..+")
if region then
-- use region
end
in my addons for years, had no complaints from users so I'd guess it works
Edit: Install locale is irrelevant, you can be playing in the eu region and have a deDE or frFR locale client.