In 'Silver Jack' one of the protagonists cries out

Stack yer duds and cut your capers, there aint no flies on me.

after being challenged to a fistfight.

I gather that duds are clothes, or at least overclothes that might inhibit movement.

But what are capers, and what do flies have to do with anything?

From the context of the song of course you can easily see that the gist of the comment is 'Bring it on if you think you got something chump, I aint going anywhere'.

Best regards.

Jack (not silver)