使用sys.obejcts进行预检查时运行的SQL脚本出现错误

我想编写一个脚本，它的功能是创建一个存储过程，在创建脚本之前，脚本必须先检查它是否存在于数据库中，因此我编写如下程序，如果我注释掉脚本将创建的前两行如果存储过程不存在，则过程成功，但是我添加了前两行，SSMS将抛出错误： 错误消息如下：

Msg 156, Level 15, State 1, Line 4
Incorrect syntax near the keyword 'PROCEDURE'.
Msg 137, Level 15, State 2, Line 69
Must declare the scalar variable "@dbname".
Msg 137, Level 15, State 2, Line 70
Must declare the scalar variable "@dbname".
Msg 137, Level 15, State 2, Line 79
Must declare the scalar variable "@DBName".
Msg 137, Level 15, State 2, Line 90
Must declare the scalar variable "@DBName".
Msg 137, Level 15, State 2, Line 105
Must declare the scalar variable "@backuppath".
Msg 137, Level 15, State 2, Line 116
Must declare the scalar variable "@dbname".
Msg 137, Level 15, State 2, Line 177
Must declare the scalar variable "@dbname".
Msg 137, Level 15, State 2, Line 184
Must declare the scalar variable "@dbname".
Msg 137, Level 15, State 2, Line 198
Must declare the scalar variable "@dbname".
......

如果我想进行预检查，谁能为我解释一下如何解决此问题？