DOC: single string vs. list of strings in `@()`

docs/tutorial.rst

@@ -502,6 +502,12 @@ result is automatically converted to a string. For example,
     42 yo
     >>> echo "hello" | @(lambda a, s=None: s.read().strip() + " world\n")
     hello world
+    >>> @(['echo', 'hello world'])
+    hello world
+
+.. warning::
+    If the expression is a string and not a list then it will be passed to the
+    subprocess as a single argument.
 
 This syntax can be used inside of a captured or uncaptured subprocess, and can
 be used to generate any of the tokens in the subprocess command list.

news/doc_at_cmd.rst

@@ -0,0 +1,14 @@
+**Added:**
+
+* Docs for using ``@(<expr>)`` as a way to run commands and a gotcha about
+  list of strings vs single string expressions.
+
+**Changed:** None
+
+**Deprecated:** None
+
+**Removed:** None
+
+**Fixed:** None
+
+**Security:** None