x := strip_first_letter(strip_first_letter(strip_first_letter(x)));

function strip_first_letter(in_p in varchar2) return varchar2 is
begin
   ...
end;
/

function strip_first_letter(
                               in_p in varchar2
                              , out1_p out varchar2
                              , out2_p out varchar2
                              , out3_p out varchar2
                            ) return varchar2 is
begin
   ...
end;
/

 create or replace function fnProduct ( A in number , Res Out number ) return number
     is
    begin
       res := a * 10;
       return res;
     end;
    /

Function created.


var A number;
var R number;

set serverout on 

exec :A  := fnProduct (100,:R );


exec  dbms_output.put_line(:R);

1000

PL/SQL procedure successfully completed.

Elapsed: 00:00:00.56
SQL> create or replace function fnProduct ( A in number , Res Out number,Res1 Out number ) return number
  2       is
  3      begin
  4         res := a * 10;
  5         res1 := a * 100;
  6         return res;
  7       end;
  8      /

Function created.

Elapsed: 00:00:00.54
SQL> 
SQL> var A number;
SQL> var B number;
SQL> var C number;
SQL> set serverout on
SQL> 
SQL> exec :A  := fnProduct (100,:B,:C );

PL/SQL procedure successfully completed.

Elapsed: 00:00:00.53
SQL> exec  dbms_output.put_line(:B || ' , ' || :C);
1000 , 10000

PL/SQL procedure successfully completed.

Elapsed: 00:00:00.53
SQL>