The extended JSON data type REGULAR_EXPRESSION is not supported

Summary:

I have an application that uses the MongoDB API for Autonomous JSON Database. I was attempting to do a case-insensitive find query on a collection using regex but came across the error The extended JSON data type REGULAR_EXPRESSION is not supported. After doing some research, I found out that regex fields aren't supported by the MongoDB API. In this case, how would I perform a case-insensitive search on this data? For context, the field I am trying to search in is an array, like so:

variants: [ "Hello", "hi", "hey" ]

I just need to do a search to find if a word exists in this array, without taking case into account.