如何在 initial / task 等 begin_end 中等待某一个信号

initial begin
    clk = 0;
    rst = 1;
    start = 0;
    #50
    rst = 0;
 
    #50
    start = 1;
    #20
    start = 0;
    
   @(osc_over); //wait for first over
    #100
    start = 1;
    #20
    start = 0;    
end

要用

        @(sensitive_sign) ;    //注意加结束分号 

也可以边沿敏感   

        @(posedge  sensitive_sign) ;    //注意加结束分号 

由此可见 @ 即为等待