Yes, oNdizZ is correct.
To make a region, you would simply do:
JASS:
local region r = CreateRegion()
But what GUI creates is not a region, but a rect, which is literally the same but GUI uses it for its stuff.
While if you wanted to create a Rect (Which is GUI version), then you would use:
JASS:
local rect r = Rect(MinX, MinY, MaxX, MaxY)
Regions use cells while rects dont, rects just use the Min/Max X/Y.
And both of rects and regions have theyre remove functions.
JASS:
native RemoveRect takes rect whichRect returns nothing
native RemoveRegion takes region whichRegion returns nothing
Dont get confused with deallocatation, you merly need to remove the handle (such as a effect, a region, rect, unit or whatever), but setting a variable to null will deallocate the variable, not the handle. You need to remove and set to null to be clear of memory leaks.
Example:
JASS:
local rect r = Rect(...)
call DoStuffWithRect(...)
call RemoveRect(r)
set r = null
