diff -r 48743ad2d2ef Doc/reference/simple_stmts.rst
--- a/Doc/reference/simple_stmts.rst	Tue May 10 19:16:03 2011 +0200
+++ b/Doc/reference/simple_stmts.rst	Tue May 10 16:53:59 2011 -0400
@@ -980,8 +980,8 @@
 This statement supports dynamic execution of Python code.  The first expression
 should evaluate to either a string, an open file object, or a code object.  If
 it is a string, the string is parsed as a suite of Python statements which is
-then executed (unless a syntax error occurs). [#]_  If it is an open file, the file
-is parsed until EOF and executed.  If it is a code object, it is simply
+then executed (unless a syntax error occurs). [#]_  If it is an open file, the
+file is parsed until EOF and executed.  If it is a code object, it is simply
 executed.  In all cases, the code that's executed is expected to be valid as
 file input (see section :ref:`file-input`).  Be aware that the
 :keyword:`return` and :keyword:`yield` statements may not be used outside of
@@ -992,7 +992,12 @@
 current scope.  If only the first expression after :keyword:`in` is specified,
 it should be a dictionary, which will be used for both the global and the local
 variables.  If two expressions are given, they are used for the global and local
-variables, respectively. If provided, *locals* can be any mapping object.
+variables, respectively. If provided, *locals* can be any mapping object.  When
+the code contains only the first expression after :keyword:`in` 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.
 
 .. versionchanged:: 2.4
    Formerly, *locals* was required to be a dictionary.