Oracle 11g Release 2

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create table mytable (col1, col2, col3, col4, col5) as
select 1, 2, 3, 'test', sysdate from dual;
1 rows affected

create or replace package mypackage as 
  function myfunction (param1 number, param2 number, param3 number)
  return mytable%rowtype;
end mypackage;
/
create or replace package body mypackage as 
  function myfunction (param1 number, param2 number, param3 number)
  return mytable%rowtype is
    l_row mytable%rowtype;
  begin
    select * into l_row
    from mytable
    where col1 = param1
    and col2 = param2
    and col3 = param3;

    return l_row;
  end myfunction;
end mypackage;
/
select mypackage.myfunction(1, 2, 3) from dual;
ORA-06553: PLS-801: internal error [55018]

declare
  l_row mytable%rowtype;
begin
  -- call the function and assign the result to a variable
  l_row := mypackage.myfunction(1, 2, 3);
  -- do something with the result
  dbms_output.put_line(l_row.col4 ||':'|| l_row.col5);
end;
/
1 rows affected

dbms_output:
test:29-APR-19