How do I conditionally create a stored procedure in SQL Server?

Here's what I came up with:

Wrap it in an EXEC(), like so:

if @version <> @expects
    begin
        ...snip...
    end
else
    begin
        exec('CREATE PROC MyProc AS SELECT ''Victory!''');
    end

Works like a charm!

SET NOEXEC ON is good way to switch off some part of code

IF NOT EXISTS (SELECT * FROM sys.assemblies WHERE name = 'SQL_CLR_Functions')
  SET NOEXEC ON
GO
CREATE FUNCTION dbo.CLR_CharList_Split(@list nvarchar(MAX), @delim nchar(1) = N',')
RETURNS TABLE (str nvarchar(4000)) AS EXTERNAL NAME SQL_CLR_Functions.[Granite.SQL.CLR.Functions].CLR_CharList_Split
GO
SET NOEXEC OFF

Found here: https://codereview.stackexchange.com/questions/10490/conditional-create-must-be-the-only-statement-in-the-batch

P.S. Another way is SET PARSEONLY { ON | OFF }.