1*956e45f6SSimon J. Gerraty# $NetBSD: ternary.mk,v 1.2 2020/10/24 08:34:59 rillig Exp $ 2db29cad8SSimon J. Gerraty 3db29cad8SSimon J. Gerratyall: 4db29cad8SSimon J. Gerraty @for x in "" A= A=42; do ${.MAKE} -f ${MAKEFILE} show $$x; done 5db29cad8SSimon J. Gerraty 6db29cad8SSimon J. Gerratyshow: 7db29cad8SSimon J. Gerraty @echo "The answer is ${A:?known:unknown}" 8db29cad8SSimon J. Gerraty @echo "The answer is ${A:?$A:unknown}" 9db29cad8SSimon J. Gerraty @echo "The answer is ${empty(A):?empty:$A}" 10