_destroy

The optional _destroy function has two basic properties:

is automatically called once the variable goes out of scope
it does not take any parameters

Defining it in the context of Point2D has no meaning, but we can use it to illustrate how it works:

TYPE Point2D
  x AS SINGLE
  y AS SINGLE
  
  FUNCTION _create(x AS SINGLE, y AS SINGLE)
    ME.x = x
    ME.y = y
    msgBox strFormat$("Point2D Variable is being created with x = {1}, y = {2}", ME.x, ME.y)
  END FUNCTION
  
  FUNCTION _destroy()
    msgBox "Point2D Variable is being released"
  END FUNCTION  
END TYPE

msgBox "Hello, I am about to call MyFunction"

MyFunction()

msgBox "Hello, I finished calling MyFunction"

FUNCTION MyFunction()
  DIM p AS Point2D(1, 2)
END FUNCTION