Very little, if any, of the scripting language as it was in 6.03 has changed to the point that it breaks in 6.12. $submenu was broken in a previous 6.1x release and then fixed again in 6.12. Unless you use DLLs your script will probably run fine without any changes whatsoever. And even if you do use DLLs there's probably a new version for them out by now so your actual script probably won't need changing anyway.
Your reasons for not upgrading don't make sense - yes you'll have to test your script again, but you have to do that for every new version - it's not like 6.12 is some magical version which breaks scripts whereas no other update has ever done so. Do you think that anytime someone releases a script of addon they should demand that mIRC never change from that moment because it might break their script?
