1
 2.RECIPEPREFIX := |
 3all:
 4|       $(MAKE) -f t001.mk foo
 5foo:
 6|       @echo $(MAKE)
 7|       @echo MAKELEVEL = $(MAKELEVEL)
 8|       $(MAKE) -f t001.mk last
 9last:
10|       @echo $(MAKE)
11|       @echo MAKELEVEL = $(MAKELEVEL)
12|       @echo THE END