We have a field in one of our templates that will correctly format and enter the static elements from the regular expression from the constraint.  For example if you put in "T \d\d R \d\d" as a constraint, the field will prefill "T  R  " in the field when entering the template.  We need to expand one of the digits in the field, but to make it work we need to make one of the digits optional. For example "T \d\d R \d\d\d?".  Once we do that it quits prefilling the field with the "T   R  ". Does anyone know of a way to keep it prefilling the field, while having an optional digit in the regex?