FWIW, it's preferable if you do

  my $qry = qq(select contador, cod_entidad_oim, cod_agr, cod_operacio
+n from mapcom_portext.TR0685002  where fch_hor_operacion between to_d
+ate(?,'dd-mon-yyyy') and to_date(?,'dd-mon-yyyy'));
[download]

and later

  my $sth = $dbh->prepare($qry);
  $sth->execute($now, $onehourago);
[download]

... etc. (just in case)...