I have always used it this way:

ifndef MAKECMDGOALS
        @echo "$$(MAKECMDGOALS) is not defined"
    else 
        @echo "$(MAKECMDGOALS) is defined"
    endif

No parentheses, or "$" sign. A lesson hard learned, or was it? What is the difference in these two syntaxes?

ifndef $(MAKECMDGOALS)
        @echo "$$(MAKECMDGOALS) is not defined"
    else 
        @echo "$(MAKECMDGOALS) is defined"
    endif