gistfile1.py

words = { word.strip(): None for word in open('/usr/share/dict/words') }
four = [word for word in words.keys() if len(word) == 4]

for left in four:
    for right in four:
        combined = ''.join([ left[j] + right[j] for j in range(4) ])
        for word in words:
            if not combined.startswith(word):
                continue
            rest = combined[len(word):]
            if not rest or rest in words:
                print left, right, word, rest