I agree with Khaled about not coding something that has to detect different language strings or which uses e.g. modes which are not standardised.
But as posted in a comment above, I believe that this can be coded without either of these based only on:
1. User's mIRC Server settings for automated authentication;
2. Use of Nickserv response strings which are NOT language specific (like "/msg Nickserv" which are IRC commands and don't differ between languages) to identify Notices from Nickserv that should be ignored.
3. Assuming that user's mIRC server settings are correct and server is working correctly (which will be true 99.9% of the time) and so user will be authenticated ok and assuming that Nickserv notices not ignored by 2. are confirming authentication - but handling with a lengthy timeout the situation when this is not the case. (If Notice is a failed authentication, then we should still attempt a /join.)
With this approach you will not need to code for:
- Language strings
- User modes