The NLP modules are generally found in the "Lingua" namespace - most of the various part-of-speech taggers, lemmatizers, stemmers etc. have a Perl implementation.

Some examples:
Lingua::EN::Tagger
Lingua::TreeTagger
Lingua::FreeLing3
Lingua::EN::SENNA
Lingua::CollinsParser
Lingua::BrillTagger

If you are going to do further NLP type analysis they are worth looking into.