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Regex falls outside the scope of our support. This means that we’re unable to help further with setup or troubleshooting. Additionally, with a code-based solution, we can’t guarantee its functionality or full compatibility with Knack.

While we can’t help further, there are many resources that can point you in the right direction:

You can ask for help in our community of other Knack users.
You can learn about, write, and test regex at https://regex101.com/. Use the ECMAScript/Javascript option.
Share your question in external developer communities such as Stack Overflow.