1# http://www.gnu.org/software/make/manual/make.html#Syntax-of-Functions
 2comma:= ,
 3empty:=
 4space:= $(empty) $(empty)
 5foo:= a b c
 6bar:= $(subst $(space),$(comma),$(foo))
 7# bar is now `a,b,c'
 8
 9test:
10	echo $(bar)
11	echo $(subst ,repl,str)