The reach of a range is the range with the exclusion of all the ranges contained within it.
begin
{ A }
begin
{ X }
end
{ B }
begin
{ Y }
end
{ C }
end
In the example above, A, B and C are in the reach
of the range introduced by the top-level serial clause, while X
and Y are in the reach of their respective containing serial
clauses.
Note that X and Y are in the range established by the
top-level serial clause, but not in its reach.