Just to clarify a bit, since this seems to be confusing sometimes:
To treat a variable as a global, you must EITHER declare it as global in every script and handler where it is used, such as:
set point to (x,y) -- uses global x and y
OR you must use the word global before the variable name every time it is used, like this:
set point to (global x, global y)
You can use whichever approach you like (or even both, although once a variable has been declared as global in a handler, there is no need to use the word global before the name within that handler).
The exact same rules apply to universal variables (which retain their values across multiple runs during the same Eggplant session).