How do you plan to solve it?
module dff_async_reset_preset ( input CLK, input RST, input PRE, input D, output reg Q ); always @(posedge CLK, posedge RST, posedge PRE) begin if (RST) Q <= 1'b0; else begin if (PRE) Q <= 1'b1; else Q <= D; end end endmodule