def dropWhileSame = { from, to ->
  def pair = [from.toList(), to.toList()]
  while(pair.every()) {
    def head = pair*.head()
    if (head.every{head.first() == it}) pair = pair*.tail()
    else break
  }
  pair*.join()
}

assert ['aaa/bbb/ccc', 'ddd/eee/fff'] == dropWhileSame(
  '/Users/fumo/work/aaa/bbb/ccc',
  '/Users/fumo/work/ddd/eee/fff'
)