I think you should just ignore occursin, and use contains. If I don’t misremember, the latter simply replaces the former, and occursin is mostly around for backwards compatibility.
I’m not so sure in should work on substrings. I would rather see a dedicated operator for this.
Oh, BTW, this post: Please read: make it easier to help you has some good tips on writing posts. In particular, it shows you how to include formatted and inline code, so you don’t have to use e.g. bold.