a 1MHz clock, and you want to toggle the led once per secon

reg [31:0] count;
reg        led_state;
wire count_max = 32'd1_000_000;


assign count_nxt = (count >= count_max) ? 32'd0 : count + 32'd1;
assign led_state_nxt = (count == count_max) ? ~led_state : led_state;

always @(posedge clk)
begin
    count <= count_nxt;
    led_state <= led_state_nxt;
end