with a comma (marked in red) , you'll get an insufficient parameter error. Without the comma, it returns the variable name only.

i dont think i do it many times and that's work

test this

alias t {
  var %x $+ $me 1
  echo 4 -a evaluated 1: $(,$+(%,x,$me))
  echo 6 -a evaluated 2: $($+(%,x,$me),2)
  echo 3 -a not eval. 1: $+(%,x,$me) 
  echo 5 -a not eval. 2: $+(%x,$me) 
  if $(,$+(%,x,$me)) { echo -a test ok for evaluation }
}