You didnt explained what this is made for
but this same script can be done using the .pnick property

The pnick property returns the nickname in a .@%+nick format.

from help file

just an advice, you can write the same script using

alias hl {
  msg # $regsubex($str($chr(32),$nick(#,0)),//g,$nick(#,\n).pnick)
}

or

alias hl {
  var %x = 1,%y 
  while ($nick(#,%x)) {
    %y = %y $chr(32) $nick(#,%x).pnick
    inc %x
  }
  msg # %y
}