Oracle 18c

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create table t1 (col1, col2) as
select 1, 'one' from dual
union all
select 2, 'two' from dual
2 rows affected

create table t2 (pk number primary key, col1 number, col2 varchar2(10));
declare
  l_col1 t1.col1%type;
  cursor l_cursor is
    select col1 from t1 order by col1;
begin
  open l_cursor;
  loop
    fetch l_cursor into l_col1;
    exit when l_cursor%notfound;
    dbms_output.put_line('l_col1: ' || l_col1);
    for r in (
      select rownum as rn, col1, col2 from t1 where col1 = l_col1
    )
    loop
      dbms_output.put_line('  r.rn ' || r.rn || ' col1 ' || r.col1 || ' col2 ' || r.col2);
    end loop;
  end loop;
  close l_cursor;
end;
/
1 rows affected

dbms_output:
l_col1: 1
  r.rn 1 col1 1 col2 one
l_col1: 2
  r.rn 1 col1 2 col2 two

declare
  l_col1 t1.col1%type;
  cursor l_cursor is
    select col1 from t1 order by col1;
begin
  open l_cursor;
  loop
    fetch l_cursor into l_col1;
    exit when l_cursor%notfound;
    dbms_output.put_line('l_col1: ' || l_col1);
    for r in (
      select rownum as rn, col1, col2 from t1 where col1 = l_col1
    )
    loop
      dbms_output.put_line('  r.rn ' || r.rn || ' col1 ' || r.col1 || ' col2 ' || r.col2);

      insert into t2 (pk, col1, col2)
      values (r.rn, r.col1, r.col2);

      dbms_output.put_line('inserted ' || sql%rowcount || ' rows');
    end loop;
  end loop;
  close l_cursor;
end;
/


dbms_output:
l_col1: 1
  r.rn 1 col1 1 col2 one
inserted 1 rows
l_col1: 2
  r.rn 1 col1 2 col2 two

ORA-00001: unique constraint (FIDDLE_MMRTNCSWTDQLIXBBNSCV.SYS_C00257071) violated
ORA-06512: at line 17
ORA-06512: at line 17