Quoting when passing variables via $(MAKE)

[Greg Chicares]

In the example below, shouldn't
  foo='$(foo)'
with single quotes pass the string
  $(foo)
itself, instead of its value?

$cat pass_options.make
foo = xyz

.PHONY: all
all:
        $(MAKE) -f receive_options.make foo=$(foo)
        $(MAKE) -f receive_options.make foo='$(foo)'
        $(MAKE) -f receive_options.make foo="$(foo)"

$cat receive_options.make
.PHONY: all
all:
        echo foo is $(foo)

$/tmp/make-3.81beta4/make -s -f pass_options.make
foo is xyz
foo is xyz
foo is xyz

I'm using beta4, but older versions seem to work the same way.