- You have right side forward. Your opponent has left side forward (mirror stance).
- Your throw a right jab.
- Your opponent uses leading left arm to block your punch to your left (his right).
- You spin your right arm, change your jab into a hook, and punch on the left side of his head.
It's similar to the "right low hook to the chest, right high hook to the head" combo. You just replace your 1st low hook to a jab. Sometime the opening that you have just created is easier for your leading arm to punch again than to use your back arm to punch.
For clarification, for those who might not be familiar with this sort of approach:
This is something I think any CMA practitioner is used to -- reusing a limb that is already extended.
I think most striking arts, however, tend not reuse an extended hand and always retract before throwing another punch. This is why generating power over a short distance is emphasized in most CMA styles, where it may not be in other arts.
We do many similar things in Wing Chun, even if we don't necessarily employ a hook. If a block crosses your centerline, you can roll it across with your elbow and straight punch, or back fist, or even come around from the outside with another punch, be it straight or circular in nature, as Wang describes. Likewise, if an opponent blocks your hand to the outside, you can circle around to the inside to deliver a straight or upper cut. Or, in either case, you can clear the line with your rear hand by grabbing and pulling, pressing, slapping, or just delivering a second very quick straight punch as your opponent crosses centerline (the last being my absolute favorite technique when playing with Karate guys who sometimes are in the habit of blocking across center / further than is necessary).
It's important to note that none of these things rely on visual perception and reaction time. They rely instead on touch, which is processed much quicker by the brain. So essentially, you throw an attack on a line that covers you and threatens your opponent; if you feel something intercepts it, then you instinctively respond via feeling, in that same moment, in order to clear the way continue attacking and cover the line or position yourself against the next hand that will come.
This all requires a relaxed nature and sensitivity training to develop.
This is just offering a bit of elaboration on the CMA approach, for anyone who might not be following Wang's thinking.