I'd like to use the dialplan module to remove all non-digits from a string.  For example, "1-306-555-1234" becomes "13065551234" and "(306) 555-1234" becomes "3065551234".

Unfortunately, I can't figure out the regular expressions for subst_exp and repl_exp.  I can easily replace one instance of a non-digit, however I can't figure out how to replace all non-digits.

-H