Why doesn't bubble allow a constraint of "Starts With?"

I need to create a constraint that for “Starts With” but it doesn’t exist. I have two “Contains” constraints that get their values from a couple of inputs. In one I would enter what I was filtering to started with, and the other one was another part of a field value it needed to contain. Worked great until what I started with like S- also occasionally occurred again. What’s the trick to accomplishing this? This seems like something that would be a most basic bubble function.

Use truncate.
msedge_f53korENK5
This gives me the value “h” because the first letter of the string is “h” from “https://sdkjlfhsaldkjf

truncate to 1 then filter based off that.