This is a topic made to include commonly-asked-for functions such as those that edit lists but without sorting or duplicates.
This takes %0, and removes duplicate items and items in %1.
It works by creating a list comprised of the non-duplicated items of %0 without the items from %1 (This is the setdiff() in the second argument).
This list is then passed to the munge(), which has the list in original order (%0).
The items of the third argument (a copy of the second) are rearranged according to the order of the original list supplied in the first.