[DahkCeles]

Totally agree with the previous post; just providing examples with and without the square brackets:


/cast [modifier:SELFCAST, @player] [@mouseover] [ ] Greater Heal

if my selfcast modifier key is pressed then
    cast Greater Heal on myself
elseif my mouse is over a unit then
    cast Greater Heal on the moused-over unit
else
    cast Greater Heal
end

/cast [modifier:SELFCAST, @player] [@mouseover] Greater Heal

if my selfcast modifier key is pressed then
    cast Greater Heal on myself
elseif my mouse is over a unit then
    cast Greater Heal on the moused-over unit
end

So adding the empty square brackets provides a "fallback" to still cast a spell even if you didn't have a modifier key pressed nor a mouseover target.