How do you plan to solve it?
module t_ff_async_pr ( input CLK, input RST, input PRE, input T, output reg Q ); always @(posedge CLK or posedge RST or posedge PRE) begin if(RST) Q<=1'b0; else begin if(PRE) Q<=1'b1; else case({T}) 1'b0:Q<=Q; 1'b1:Q<=~Q; endcase end end endmodule