'Idha, bhikkhave, bhikkhu kāye kāyānupassī viharati ātāpī sampajāno satimā vineyya loke abhijjhādomanassaṃ.'
'Here, almsmen, an almsman looking into body dwells in body as the ardent aware recollector would remove the avarice and distress about the world.' (AN4.274)
If you watch television, you can dwell in it. If you look at the past, you can dwell in it. But not while you keep track of your current surrounding. So in order to dwell in them this surrounding will have to make room first. And how it this done? By loosing interest in it.
Like that; with the removal of the avarice and distress, all interests and concerns about the world are gone and the world disappears for one. What then remains to dwell in is body, that is if what is looked into is body. Likewise we can dwell in feelings when what is looked into are feelings. So this text does not differ so much from other texts like in MN121. Thus with the perception of the world gone, the remaining non-emptiness is the perception of body, with the perception of body gone, the remaining non-emptiness is the perception of feelings ... mind ... principles. It is just this emptying, stepping back, withdrawal, gradual stilling.