# Ask for errors at database handle creation
my $dbh2 = DBI->connect(
  $dsn, $user, $password,
  { RaiseError => 1, AutoCommit => 0 }
);

# Or check your method call
$dbh2->do($sql) or die "Cannot execute SQL '$sql': $DBI::errstr;

##</code><code>##

  $dbh2->do(
    qq{alter session set nls_timestamp_format = 'YYYY-MM-DD HH24:MI:SS'}
  ) or die "Can't set timestamp format: $DBI::errstr";