1files = $(wildcard *,*)
 2
 3# test expectes empty, since no *,* found.
 4test:
 5	echo $(files)
 6	touch foo,bar
 7
 8# when foo,bar doesn't exit, "make test2" report empty.
 9# next "make test2" reports "foo,bar".
10test2: foo,bar
11	echo $(files)
12
13foo,bar:
14	touch foo,bar