Cant define SQL variable when using WITH statement

Question

This sql is valid:

 WITH A AS
 (SELECT TOP 1000 * 
  FROM dbo.SomeTable)

 SELECT * FROM A

While this one gives an error(Incorrect syntax near the keyword 'DECLARE'):

WITH A AS
(SELECT TOP 1000 * 
 FROM dbo.SomeTable)

 DECLARE @dt DATETIME 

 SET @dt = GETDATE()
 SELECT * FROM A

 PRINT DATEDIFF(SS,GETDATE(),@dt)

Why?

Answer 1

Just do

DECLARE @dt DATETIME;

SET @dt = GETDATE();

WITH A
     AS (SELECT TOP 1000 *
         FROM   dbo.SomeTable)
SELECT *
FROM   A;

PRINT DATEDIFF(SS, GETDATE(), @dt);

The only valid thing following a CTE definition is a single statement using it

Answer 2

A CTE must be followed by a single SELECT, INSERT, UPDATE, or DELETE statement that references some or all the CTE columns. A CTE can also be specified in a CREATE VIEW statement as part of the defining SELECT statement of the view.

http://msdn.microsoft.com/en-us/library/ms175972.aspx