http://snowball.tartarus.org/algorithms/porter/stemmer.html
Arguably a bit tidier than the example Haskell version given on the Snowball web pages.
The test input was shamelessly taken from kristopolous' fine Javascript implementation,
https://github.com/kristopolous/Porter-Stemmer
foo$ runhaskell Setup configure
foo$ runhaskell Setup build
...
foo$ dist/build/checker/checker
...
# Should you so wish...
foo$ runhaskell Setup install
--sof 10/2013.