Commands that perform queries or list objects typically set the query selection set. The selection set represents the results of the previous query and the order in which the objects were displayed in the previous command. The output from these commands is numbered by default. You can refer to objects in the selection set by using:
where n is the number of the displayed object from a previous query. For example, @1 refers to the first object, @2 the second object and so on.
where n and m are the numbers of displayed objects from a previous query, and where m is greater than or equal to n. This refers to the n'th to m'th object, inclusive. For example, @2-5 refers to the second through fifth object, inclusive; @3-@6 refers to the third through sixth object, inclusive.
This refers to all of the objects in the query selection set.