88. Parallel-In Serial-Out Register

How do you plan to solve it?

module piso4 (
    input        CLK,
    input        RST,
    input        LOAD,
    input  [3:0] D,
    output reg   serial_out
);
    // Write your code here
    reg [3:0] SR;
    always @(posedge RST or posedge CLK) begin
        if(RST==1'b1) begin
            serial_out<=1'b0; 
            SR<=4'b0000;
        end
        else if(LOAD==1'b0) begin
            serial_out<=SR[0];
            SR<={1'b0,SR[3:1]};
        end
        else if(LOAD==1'b1)begin
            SR<=D;
        end
    end
endmodule