See 
PublishedAPI for packages intended to be used by Plugin and Contrib authors, or 
browse all packages.
See also 
Developing plugins, 
Developer's Bible, 
Technical Overview
 ObjectMethod onSave() 
This routine is called during the Save wizard, for any key that being
saved, regardless of whether or not it has actually changed.  This
is enabled by including the ONSAVE key in the Spec. (In this case it is
automatically enabled by the 
Pluggable/LANGUAGES.pm
This will remove the languages.cache file from the 
WorkingDir, so that
the cache can be regenerated.
If compression is enabled, it also compresses the language file.