[kovidgoyal]

Here you go, I haven't really tested it, so you might have to adjust it a little:

import regex
from calibre import replace_entities, prepare_string_for_xml

def replace(match, number, file_name, metadata, dictionaries, data, functions, *args, **kwargs):
    def fix_word(m):
        word = m.group()
        if dictionaries.recognized(word):
            return word
        for i in xrange(1, len(word) - 1):
            a, b = word[:i], word[i:]
            if dictionaries.recognized(a) and dictionaries.recognized(b):
                return a + ' ' + b
        return word
    text = replace_entities(match.group(1))
    text = regex.sub(r'\b\w+\b', fix_word, text, flags=regex.VERSION1)
    text = prepare_string_for_xml(text)
    return '>' + text + '<'

Use it with the find expression

>([^<]+)<