ngspice/examples/loops/loop_IfThenElse.cir

example if then else loop
.control

foreach val -40 -20 0 20 40
  if $val < 0
    echo variable $val is less than 0
  else
    echo variable $val is greater than or equal to 0
  end
end

let vec = 1
if vec = 1 ; $&vec = 1     is possible as well
  echo vec is $&vec
end

.endc

.end