problems with $$

[PATTON, BILLY \(SBCSI\)]

I have the following example :
INCLUDE := -Idogs -Ipigs -Isheep -Irats

PC_TO_O = @echo $$(INCLUDE:-I=include\=)

.PHONY : x

define x
x : ; $(PC_TO_O)
endef
$(eval $(call x))



It need to print out
include=dogs include=pigs include=sheep include=rats