doc: explain how to enable debug for multiple modules (#41719)

t-bltg · web-flow · commit d066a8eab3e7 · 2021-07-28T14:16:58.000-04:00
diff --git a/stdlib/Logging/docs/src/index.md b/stdlib/Logging/docs/src/index.md
@@ -217,6 +217,9 @@ julia> foo()
 
 ```
 
+Use a comma separator to enable debug for multiple
+modules: `JULIA_DEBUG=loading,Main`.
+
 ## Examples
 
 ### Example: Writing log events to a file
