This is a list of value pairs.
 Examples:

PROC: FIC - causes an item in the Processing Center location to be updated into the Fiction location on check in.
FIC: GEN - causes an item in the Fiction location to be updated into the General stacks location on check in.
_BLANK_:FIC - causes an item that has no location to be updated into the Fiction location on check in.
FIC: _BLANK_ - causes an item in location FIC to be updated to a blank location on check in.
_ALL_:FIC - causes all items to be updated into the Fiction location on check in.
PROC: _PERM_ - causes an item that is in the Processing Center to be updated to it's permanent location.

General rule: if the location value on the left matches the item's current location, it will be updated to match the location value on the right.
Note: PROC and CART are special values, for these locations only can location and permanent_location differ, in all other cases an update will affect both. Items in the CART location will be returned to their permanent location on checkout.

The special term _BLANK_ may be used on either side of a value pair to update or remove the location from items with no location assigned.
The special term _ALL_ is used on the left side of the colon (:) to affect all items.
The special term _PERM_ is used on the right side of the colon (:) to return items to their permanent location.