Someone

on *:text:!dm*:#: {
  if (%dm2 == active) {
    msg $chan 10There is already a dm going on, please wait for it to end.
  }
}
if (%dm == active) {
  set %player2 $nick
  msg $chan 10The dm is set! %player1 vs. %player2 $+ .
  msg $chan 10 $+ %player1 goes first!
  set %dm2 active
  set %p1hp 99
  set %p2hp 99
  set %spec1 0
  set %spec2 0
  set %spec3 0
  set %turn 1
}
else {
  set %dm active
  set %player1 $nick
  msg $chan 10 $+ $nick has initiated a dm. Type !dm if you want to fight him/her.
}