it can easily be done without scripts if you accept some minor limits.
the trick is to create the darkness with a picture that covers the entire screen and is completely black, with only the center area being transparent - to whatever distance you want, and that includes partial darkness by changing the amount of transparent pixels between the black pixels.
the disadvantage here is that it requires the player to stay in the center of the window - he cannot be allowed to approach the borders of the map.
and that requires to make the maps at least 10 tiles larger in any direction, while blocking all places where the player might be able to get nearer than 9 tiles to the border.