Updated SC2163 (markdown)

SC2163.md

@@ -1,4 +1,4 @@
-## Exporting an expansion rather than a variable.
+## This does not export 'FOO'. Remove $/${} for that, or use ${var?} to quiet.
 
 ### Problematic code:
 
@@ -20,9 +20,18 @@ export MYVAR
 
 ### Exceptions:
 
-If you do want to export the variable's value, e.g. due to indirection, you can disable this message with a directive:
+If this is intentional and you do want to export `foo` instead of `MYVAR`, you can either use a directive:
 
 ```sh
 # shellcheck disable=SC2163
 export "$MYVAR"
 ```
+
+Or after (but not including) version 0.4.7, take advantage of the fact that ShellCheck only warns when no parameter expansion modifiers are applied:
+
+```sh
+export "${MYVAR}"    # ShellCheck warns
+export "${MYVAR?}"   # No warning
+```
+
+`${MYVAR?}` fails when `MYVAR` is unset, which is fine since `export` would have failed too. The main side effect is an improved runtime error message in that case.