sowmya143,
I have successfully updated an existing LOBs with the following fill-in-the-blank code:

#!/usr/bin/perl
use strict;
use warnings;
use DBD::Oracle ':ora_types';

# Set up any necessary Oracle ENV variables

my $dbh = DBI->connect($conn_string, $user, $pass) or die $DBI::errstr
+;
my $sth = $dbh->prepare("UPDATE table SET field = ?") or die $dbh->err
+str;
$sth->bind_param(1, $updated_value, {ora_type => ORA_BLOB});
$sth->execute() or die $dbh->errstr;
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