如何在存储过程内调用带参数的存储过程

create   procedure   p1
@parm1   varchar(20)   output
as
set   @parm1='AAAAAA'

go

create   procedure   p2
as
declare   @tmp   varchar(20)
exec   p1   @tmp   output
select   @tmp
go

--测试
exec   p2