Bind variables can be of type IN, OUT, or IN OUT.
By default, all parameters are of type IN.
Using an OUT Parameter
SQL> declare 2 a NUMBER; 3 b NUMBER:=1; 4 c NUMBER:=2; 5 v_plsql_tx VARCHAR2(2000); 6 begin 7 v_plsql_tx := 'begin ' || ':1:=:2 -:3; ' || 'end;'; 8 execute immediate v_plsql_tx using out a, b, c; 9 DBMS_OUTPUT.put_line('a='||a); 10 end; 11 / a=-1 PL/SQL procedure successfully completed. SQL>