Make -- double :: after target

[Mark Lawrence]

I note that in some Makefiles that come with Larry Wall's good stuff
(which we use as standard templates for our projects), that some targets
have a :: after them with no dependencies, e.g.
	
	$(public)::
		@case '${MFLAGS}' in *[ik]*) set +e;; esac; \
		for i in $(DIRSTOMAKE);\
		do \
			(cd $$i ; echo "making $$i"; \
			$(MAKE)  $(MFLAGS)); \
		done

I dug into my trusty Make User's guide (from Sun) and looked for the
meaning to no avail.  Would somebody care to enlighten me via e-mail?
--
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