+ // word: skip a group of insets of the form X*(B*|R*|P*) (greedy
+ // match) where X is any math class, B is mathbin, R is mathrel, and
+ // P is mathpunct. Make sure that the following remains true:
+ // mathForward(true); mathBackward(true); mathForward(true)
+ // is the same as mathForward(true) and
+ // mathBackward(true); mathForward(true); mathBackward(true)
+ // is the same as mathBackward(true).