SQL> create or alter procedure p1 as begin end;
SQL> commit;
SQL> recreate table tlog(dts timestamp default 'now', text varchar(50));
SQL> commit;
SQL>
SQL> set term ^;
SQL> create or alter procedure p1 returns(n int) as
CON> begin
CON>   in autonomous transaction do
CON>   insert into tlog(text) values('p1 start');
CON>
CON>   select count(*) from rdb$types,rdb$types,(select 1 i from rdb$types rows 20) into n;
CON>
CON>   suspend;
CON>
CON>   in autonomous transaction do
CON>   insert into tlog(text) values('p1 finish, n='||:n);
CON>
CON> end
CON> ^ set term ;^
SQL> commit;

SQL> commit;
SQL> set term ^;
SQL> execute block as --returns(n int ) as
CON>   declare n int;
CON> begin
CON>   delete from tlog;
CON>    select n from p1  into n;
CON> end
CON> ^ set term ;^
SQL> commit;
SQL> select * from tlog;

                      DTS TEXT
========================= =====================
2014-04-25 21:57:26.5260  p1 start
2014-04-25 21:57:27.2090  p1 finish, n=1270080

SQL> commit;
SQL> set term ^;
SQL> execute block as
CON>   declare n int;
CON> begin
CON>   delete from tlog;
CON>   execute procedure p1  returning_values n; 
CON> end
CON> ^ set term ;^
SQL> commit;
SQL> select * from tlog;

                      DTS TEXT
========================= =======================
2014-04-25 21:57:42.4290  p1 start