On my day job, i needed to copy an ArrayCollection to a different var so i could manipulate it without affecting the original. Went with this:
arraycollection2 = arraycollection1;
With this method, all i did to arraycollection2 was also happening to arraycollection1.
to copy arrayCollection1 to arrayCollection2 without making it a reference:
arrayCollection2 = ObjectUtil.copy(arrayCollection1) as ArrayCollection;
Oh, and make sure you import this: