SQL>
SQL>
SQL> create or replace function first_function return varchar2 as
2 begin
3 return 'Hello World';
4 end first_function;
5 /
Function created.
SQL>
SQL>
SQL>
SQL> set serverout on
SQL>
SQL> declare
2 l_str varchar2(100) := null;
3 begin
4 l_str := first_function;
5 dbms_output.put_line( l_str );
6 end;
7 /
Hello World
PL/SQL procedure successfully completed.
SQL>