If your language has ortographic accentuation (such as Spanish, Catalan, and many other roman languages), the suffixation rules may have to deal with accent restoration when rebuilding the original roots. To do this, you have to to program a accents_mylanguage class derived from abstract class accents_module, which provides the service of restoring (according to the accentuation rules in your languages) accentuation in a root obtained after removing a given suffix.
A good idea to start with this issue is having a look at the accents_es class.