i think that with the command /play is better because if the nicklist is not yet finished another user could repeat !yell after 5 sec and execute the code again
Code:
on *:text:!yell:#:{
  if !$play(#) {
    tokenize 3 $regsubex($str(.,$nick(#,0)),/./g,$+($nick(#,\n),$chr(3)))
    write tmpfile $*
    .play # tmpfile
    .remove tmpfile
  }
}