@_(Query_Usage)

   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