module foo (
  input fifty, dollar, cancel,
  input clk, rst,
  output st, insert_coin, money_return, dispense
);

parameterINIT=0,S50c=1,VEND=2,RETURN=3;

reg [1:0] nst, st

always @ (posedge clk)
begin
  if(!rst)
    st <= INIT
  else
    st <= nst;
end

always @*
begin
  nst = st;
  case(st)
    INIT: if(fify) nst = S50c;
      if(dollar) nst = VEND;
    S50c: if(fifty) nst = VEND;
      if(dollar|cancel)