Regex operations not working when used with systems properties as blocking triggers?

I’m having trouble getting Zaraz’s triggers to work when implementing them using Match Rule with {{ }} and then using either the “Matches regex” or “Not matches regex” operation. Here’s an example:

I’m trying to use this as a blocking trigger, but Zaraz won’t recognize it. FWIW, I’ve also tried versions where I don’t escape the / (e.g. ^/(test|admin)\b. Am I missing something, or could there maybe be a bug with regex operations? Thanks!