this should return users with mode +a

on *:text:!admins:#: {
  var %a = $nick(#,0,a)
  :loop
  while (%a) {
    if ($nick(#,$nick(#,%a),a)) var %admins = $+(%a,.,$nick(#,%a)) %admins | dec %a 
    else goto loop
  }
  msg # # Admins are: %admins 
}

still useless tho, just look at your nicklist. rofl.

you also need a space between your opening bracket and your "msg"