ternary.mk revision 1.2 
11.2Srillig# $NetBSD: ternary.mk,v 1.2 2020/10/24 08:34:59 rillig Exp $
21.1Sapb
31.1Sapball:
41.1Sapb	@for x in "" A= A=42; do ${.MAKE} -f ${MAKEFILE} show $$x; done
51.1Sapb
61.1Sapbshow:
71.1Sapb	@echo "The answer is ${A:?known:unknown}"
81.1Sapb	@echo "The answer is ${A:?$A:unknown}"
91.1Sapb	@echo "The answer is ${empty(A):?empty:$A}"
10