VMS Help SCA, SCA Topics, @ (Query Usage)  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    A query usage function incorporates the results of previous
    queries into query expressions. The function has the following
    form:

    @( query_name )

    The value of this expression is that of the expression that is
    specified as query_name. The default query name is the current
    query, SCA$CURRENT_QUERY.

    You can see an example of its use in the following sequence of
    queries:

       FIND X
       FIND @(SCA$CURRENT_QUERY) AND SYMBOL=ROUTINE

    The advantage of using this notation is that the results of the
    previous query are not reevaluated. Thus the second query will be
    faster than the query:

      FIND X AND SYMBOL=ROUTINE