random limit | seed ?seedval?
              Generate a pseudorandom integer number greater than
              or equal to zero and less than limit.  If  seed  is
              specified,  then the command resets the random num-
              ber generator to a starting point derived from  the
              seedval.  This allows one to reproduce pseudorandom
              number sequences for testing purposes.  If  seedval
              is  omitted,  then the seed is set to a value based
              on current system state and the current time,  pro-
              viding  a  reasonably interesting and ever-changing
              seed.

              This command is provided by Extended Tcl.