% preprocess rule that goes from a single digit (0-9) to form to be processed in the map; this does not work for digits > 9 if they are represented as numerals, but should work if they are represented as characters.
೦ -> ಸೊನ್ನೆ / _
೧ -> ಒಂದು / _
೨ -> ಎರಡು / _
೩ -> ಮೂರು / _
೪ -> ನಾಲ್ಕು / _
೫ -> ಅಯ್ದು / _
೬ -> ಆರು / _
೭ -> ಏಳು / _
೮ -> ಎಂಟು / _
೯ -> ಒಂಬತ್ತು/ _