How to restart a fork block after disabling it?

In reply to Ariel Elliassi:

forever begin
 @(case1)
  disable fork; // does nothing the first iteration for the loop
  fork
   begin // first block
    <wait 3 clocks>
    <some code>
   end
  join_none
end

Note that you may need to add an isolating fork/join if there are other child threads spawned before the forever loop.