Make backend checking actually work properly

ptgdp

@@ -104,12 +104,15 @@ main() {
 		done < "$_optconfigfile"
 	fi
 	# Validate critical options
-	{
+	(
 		for backend in ${_supportedbackends[@]}; do
-			[ "$backend" = "${_config[backend]}" ] && return 0
+			if [ "$backend" = "${_config[backend]}" ]; then
+				return 0
+			fi
 		done
-		error "Unsupported backend: ${_config[backend]}" 50
-	}
+		return 1
+	) || error "Unsupported backend: ${_config[backend]}" 50
+
 	# Pre-really-do-stuff hooks like help text
 	[ -n "$_opthelp" ] && printhelp && exit 0