The module is a probability based, corpus-trained tagger that assigns 
POS tags to English text based on a lookup dictionary and probability 
values. The tagger determines appropriate tags based on conditional 
probabilities - it looks at the preceding tag to figure out what the 
appropriate tag is for the current word. Unknown words will be classified 
according to word morphology or can be set to be treated as nouns or 
other parts of speech.

The tagger also recursively extracts as many nouns and noun phrases as 
it can, using a set of regular expressions.

WWW: http://search.cpan.org/dist/Lingua-EN-Tagger/