Question to EXTRACT_ONLY

From: Matthias Fechner <idefix_at_fechner.net>
Date: Mon, 28 Nov 2022 18:12:31 UTC
Dear all,

I currently work on an upgrade of some ports, but to continue here, I 
need to understand what to two lines are doing:
EXTRACT_ONLY=  ${ALLFILES:Nprebuilt*:}

EXTRACT_ONLY+= ${DISTFILES:N*.mod\:*:N*.mod:C/:.*//}

Would be nice if someone could bring some light into this.

Thanks a lot
Matthias