NAME := a b c
run:
	@for tmp in $(NAME); do \
		echo $$tmp; \
	done

> cat gen.txt 
items = a b c

run:
	@line=$$(head -n1 gen.txt); \
	tile_list=$$(echo "$$line" | awk '{for(i=3;i<=NF;i++) printf " %s", $$i}'); \
	for tile in $$tile_list; do \
		echo "process tile: $$tile"; \
	done

> make
process tile: a
process tile: b
process tile: c