Looking for regex to control fields in Field Maps Designer form builder

[HBrowning]

I have a form that I have configured in Field Maps Designer, and it includes inputting emails and phone numbers.  I have searched and searched, and not seen a way to control the input to these fields on form builder. I would like to throw an alert or not allow submission if the email address doesn't have an @ sign, or if the phone numbers are too long, etc.  

The Arcade expression areas available only appear to provide control logic to whether or not the field is required, editable, visible, or to calculate an expression:

I just wanted to confirm that regex is not available through Field Maps form builder anywhere, and I am not just missing it? Note that I cannot use Survey123 for this particular project (not worth describing why), otherwise yes I would be using Survey123 Connect for this because I know that you can use regex there. 

[DavidSolari]

Unless it's hidden somewhere sneaky Arcade doesn't have any regex related functions, and that's all you have access to with the new Form specification. You'll either have to swap to Survey123 which does have more complex expression parsing or you can use Arcade functions like Find to see if a certain character appears in an answer or compare its location to another one.