I think make(1) :M / :N modifiers should deal with sets as arguments.

--------8<--------8<--------8<--------8<--------8<--------8<--------8<--------8<
INPUT=	a b c
WANTED=	a b
OUTPUT=	${INPUT:M${WANTED}}

all:
	@echo ${OUTPUT}
-------->8-------->8-------->8-------->8-------->8-------->8-------->8-------->8

This doesn't work now since :M thinks of ${WANTED} to be a single word
even if it contains whitespaces.  IMO this is inconsistent since :M
thinks of ${INPUT} as multiple words.

Masao