# $FreeBSD: head/tools/regression/bin/sh/execution/set-x3.0 222907 2011-06-09 23:12:23Z jilles $

key='must contain this'
PS4='$key+ '
{ r=`set -x; { :; } 2>&1 >/dev/null`; } 2>/dev/null
case $r in
*"$key"*) true ;;
*) false ;;
esac