Like items or substring of a field

Looking to use either the substring or like feature in cloverleaf to check the beginning of a description and if match then place a description into another field.  I know the change of a field is done in the translate or iterate function but looking to perform the substring or like option (i.e. XR Chest XRay but only looking at XR) to determine outcome or what to place into another field that the 3rd party vendor is looking for.