use DBI;
OpenDatabaseConnections(); # nothing special with RaiseError = 1
...
$dbh->{LongReadLen} = 512 * 1024; # prior to prepare, right?
$dbh->{LongTruncOk} = 1;  # frustration - like to see "something"
my $sql = "select chardata from CLOB_TEST where id = 2";
my $sth = $dbh->prepare($sql, {ora_auto_lob => 0 } );
$sth->execute();
$char_locator = $sth->fetchrow_array() 
  or die "ERROR: " . $sth->errstr . "\n";

##</code><code>##

my $chunksize = 1024;
my $offset = 1;
my $data = $dbh->ora_lob_read($char_locator, $offset, $chunksize)
  or die "ERROR: " . $sth->errstr . "\n";