Examples (using 1M or 10M frequency list from Gutenberg):

$ python segmentation.py penisland
...
(['p', 'en', 'island'], -15.638518785248923)
(['pe', 'nis', 'land'], -15.108322797049299)
(['pen', 'island'], -8.375691641879506)
(['peni', 'sl', 'and'], -14.687786244444453)
(['penis', 'land'], -9.672682030503244)
(['penisl', 'and'], -15.235864890453465)
(['penisla', 'nd'], -20.26133790488834)
(['penislan', 'd'], -24.41870399665061)
(['penisland'], -16.709351998325303)
['pen', 'island']

$ python segmentation.py therapistfinder
...
(['t', 'he', 'rapist', 'finder'], -24.748890963614368)
(['th', 'era', 'pist', 'finder'], -21.212173151805697)
(['the', 'rapist', 'finder'], -15.237632013697695)
(['ther', 'a', 'pist', 'finder'], -19.589487264674233)
(['thera', 'pist', 'finder'], -19.16492932696031)
(['therap', 'ist', 'finder'], -17.992610282256244)
(['therapi', 'st', 'finder'], -24.47141671545925)
(['therapis', 'tf', 'in', 'der'], -21.371078882293887)
(['therapist', 'finder'], -13.623547247250375)
(['therapistf', 'in', 'der'], -22.861482061222056)
(['therapistfi', 'nder'], -25.98413509261641)
(['therapistfin', 'der'], -23.10614521275257)
(['therapistfind', 'er'], -24.395855144970255)
(['therapistfinde', 'r'], -30.418703996650606)
(['therapistfinder'], -22.709351998325303)
['therapist', 'finder']

$ python segmentation.py whorepresents
...
(['w', 'ho', 'represents'], -18.14739742951673)
(['wh', 'ore', 'presents'], -15.423500721603162)
(['who', 'represents'], -7.398759138614212)
(['whor', 'ep', 'resents'], -20.08562578090216)
(['whore', 'presents'], -10.445817549886325)
(['whorep', 'resents'], -15.673004770048102)
(['whorepr', 'esents'], -23.816644005322647)
(['whorepre', 'sents'], -23.098557710539556)
(['whorepres', 'ents'], -23.31936871896465)
(['whoreprese', 'nts'], -25.459662604329512)
(['whorepresen', 'ts'], -24.458042989379624)
(['whorepresent', 's'], -28.418703996650606)
(['whorepresents'], -20.709351998325303)
['who', 'represents']

It's funny to see it *work* even with Kauderwelsch:

$ python segmentation.py zugarrivesatgaredunord

(['z', 'ug', 'arrives', 'at', 'gare', 'du', 'nord'], -32.50373110714555)
(['zu', 'g', 'arrives', 'at', 'gare', 'du', 'nord'], -29.771130940523193)
(['zug', 'arrives', 'at', 'gare', 'du', 'nord'], -27.6931533335704)
(['zuga', 'rrivesatgaredunord'], -37.43176816321052)
(['zugar', 'rives', 'at', 'gare', 'du', 'nord'], -35.27313676138066)
(['zugarr', 'ive', 'sat', 'gare', 'du', 'nord'], -35.62167660702414)
(['zugarri', 'vesat', 'gare', 'du', 'nord'], -37.06730572297619)
(['zugarriv', 'es', 'at', 'gare', 'du', 'nord'], -36.19798266766783)
(['zugarrive', 'sat', 'gare', 'du', 'nord'], -34.778801974903615)
(['zugarrives', 'at', 'gare', 'du', 'nord'], -34.347608226189784)
(['zugarrivesa', 'tg', 'are', 'du', 'nord'], -36.61899603139459)
(['zugarrivesat', 'gare', 'du', 'nord'], -34.06742498500572)
(['zugarrivesatg', 'are', 'du', 'nord'], -31.83761040103289)
(['zugarrivesatga', 'red', 'un', 'ord'], -34.25155677971655)
(['zugarrivesatgar', 'e', 'du', 'nord'], -34.7329574229286)
(['zugarrivesatgare', 'du', 'nord'], -32.353490844484725)
(['zugarrivesatgared', 'un', 'ord'], -33.482848511720604)
(['zugarrivesatgaredu', 'nord'], -30.97651206109257)
(['zugarrivesatgaredun', 'ord'], -32.2095721169088)
(['zugarrivesatgareduno', 'rd'], -33.55078317272377)
(['zugarrivesatgaredunor', 'd'], -32.66984483306061)
(['zugarrivesatgaredunord'], -29.71588408160526)
['zug', 'arrives', 'at', 'gare', 'du', 'nord']