Moves the pointer from the current position to a new position, dx pixels away horizontally and dy away vertically.

CopyMove a window

[Move] Window 1..99 (Up='-' |  Down='+')
     = MoveToEdge(Top) MoveBy(0,20) DragByScreenPercent($2$1, 0);

Saying for example "Move Window 5 Left" moves the current window by dragging the title bar left by 5 screen percentage units. MoveToEdge(Top) moves the pointer to the top edge of the current window. But dragging the pointer from this position would resize the window rather than moving it, so MoveBy(0,20) moves the pointer 20 pixels down to be over the title bar. $2 is "-" and $1 is "5", so DragByScreenPercent(-5, 0) drags the pointer left by 5 screen percentage units.