
Build a decade counter that counts from 0 through 9, inclusive, with a
period of 10. The reset input is active high synchronous, and should
reset the counter to 0. We want to be able to pause the counter rather
than always incrementing every clock cycle, so the "slowena" input if
high indicates when the counter should increment.

module TopModule (
  input clk,
  input slowena,
  input reset,
  output reg [3:0] q
);

