I've been using lazy_static until now but was trying to migrate to OnceCell. It seems I can't have a OnceCell even though I'm never calling mutable methods on the regex. I'm not even using multiple threads.

The error I'm getting is:

Any way to solve this or do I have to use OnceLock / continue using lazy_static? I don't want to add the overhead of using OnceLock if not necessary.