led_switch.v

module program # (
    // Constant
    parameter TRUE = 1'b1,
    parameter FALSE = 1'b0
)(
    input BUTTON_SOUTH,
    output LED0
);
    reg led_state;
    assign LED0 = led_state;

    always @(posedge BUTTON_SOUTH) begin
        if (BUTTON_SOUTH == TRUE) begin
            // LED0 = TRUE;
            led_state <= TRUE;
        end
        else begin
            // LED0 = FALSE;
            led_state <= FALSE;
        end
    end

endmodule