For this example statement from the CBOR RFC 8610 in section 3.8.3:

nai = tstr .regexp "[A-Za-z0-9]+@[A-Za-z0-9]+(\\.[A-Za-z0-9]+)+"

The following error is raised:

Expected rule identifier followed by an assignment token `=`, `=/`, or `=//` cddl 
Target text string must match XSD regex value in the control type