This has come up several times on the DBI users mailing list: for example, here, here, here, here, and here.

Those posts go into more details, but there are several things you can try: ensure LongReadLen is set, upgrade to the most recent version of DBD::Oracle, and ensure your DBD::Oracle has been compiled against Oracle client libs more recent than 7i.

#!/usr/local/bin/perl -w
# Paper stock preview CGI
use strict;
use DBI;
use DBD::Oracle qw(:ora_types);
use CGI;

# Set oracle home environment
$ENV{ORACLE_HOME}='/home/oracle/OraHome1';

# Connect as Oracle
my $dbh=DBI->connect("dbi:Oracle:tnsentry","user","passwd");

# Use CGI
my $q = new CGI;
my $stock_id = $q->param('stock_id');  # get paper stock id

# Find the url and image size from another table
my $sth = $dbh->prepare("select stock_url, stock_imagesize from stock 
+where stock_id=?");
$sth->execute($stock_id);
my @res=$sth->fetchrow_array();
$sth->finish;

if ($res[0] eq 'CLOB') {
  # stock image is stored directly inside the database

  $dbh->{LongReadLen}=$res[1]; # set up the CLOB retrieval size

  my $sth=$dbh->prepare("select stock_mimetype, stock_image from stock
+ where stock_id=?");
  $sth->execute($stock_id);

  my @res=$sth->fetchrow_array();

  print "Content-Type: $res[0]\n\n";  # display the image
  print "$res[1]";                    # in web browser
  $sth->finish;
} else {
  # stock image stored externally
  # ...
}
$dbh->disconnect();
[download]