diff -r 82cfbe2ddfbb Doc/library/functions.rst
--- a/Doc/library/functions.rst	Wed May 11 12:24:17 2011 -0400
+++ b/Doc/library/functions.rst	Thu May 12 11:38:54 2011 -0400
@@ -373,7 +373,12 @@
    current scope.  If only *globals* is provided, it must be a dictionary, which
    will be used for both the global and the local variables.  If *globals* and
    *locals* are given, they are used for the global and local variables,
-   respectively.  If provided, *locals* can be any mapping object.
+   respectively.  If provided, *locals* can be any mapping object.  When the
+   code contains only the global dictionary, or the same dictionary is used for
+   both the global and local variables, the code is executed in a new top-level
+   scope.  However, when two different objects are used for the global and local
+   variables, the code is executed as if it were in a class statement in a new
+   top-level scope.
 
    If the *globals* dictionary does not contain a value for the key
    ``__builtins__``, a reference to the dictionary of the built-in module