#!/bin/ksh

sed '
#Remove all characters except the digits.
        s/[^0-9]//g

#If the line does not consist of exactly 9 digits, change it
#to 9 question marks.  See p. 110 and Handout 8, p. 6 for !.
        /^.........$/!s/.*/?????????/

#Insert the two dashes.
        s/^\(...\)\(..\)/\1-\2-/
'

exit 0