Lingua::Stem - finds stems for a smallish set of languages.
Lingua::StarDict::Gen - generates StarDict dictionaries. (Might be useful.)
Lingua::StarDict itself (2004) and the StarDict project (2007) at SourceForge, hmm. (console version, dates to 2006) - This might be dead, but it's intriguing.
Lingua::YaTeA - extracts noun phrase candidates from a corpus. Definitely to be studied. Seems to have a lot of innards.
Lingua::WordNet - pure Perl WordNet. Apparently. Needs study.
Lingua::Translate - interface to a Web-accessible machine translator, e.g. Babelfish.
Lingua::Sentence - Hello, segmentation! Thanks, CPAN!