Idea:

1. Some words in dictionary start with "--", they are postfix of a word
2. When an user type a word start with "-" or "--", these candidates are displayed; no change is needed
3. When an user type a word with only one candidate, and the the candidate match the word exactly, then (s)he type a "-":
   • commit the word
   • make "-" the composing region
   • display candidates start with "-"