$sth = $dbh->prepare(<<SQL);
update mydb.dbo.table_with_text_field
    set text_field=?
    where pk=?
SQL

sub write_text($$$$) {
	my ($text_field, $table_name, $where_clause, $long_text) = @_;
	my $sth;

	# If you have a NULL value that needs updating you must first update it to some non-NULL value
	# (for example an empty string) using standard SQL before you can retrieve the CS_IODESC entry.
	#          I HATE Sybase Open Client!
	$dbh->do("update $table_name set $text_field='empty' where $where_clause");

	# first we need to find the CS_IODESC data for the data
	## print "select $text_field from $table_name where $where_clause", "\n"; # for debug!
	$sth = $dbh->prepare("select $text_field from $table_name where $where_clause");
	$sth->execute;
	while($sth->fetch) {    # don't care about the data!
		$sth->syb_ct_data_info('CS_GET', 1);
	}

	# OK - we have the CS_IODESC values, so do the update:
	$sth->syb_ct_prepare_send();
	# Set the size of the new data item (that we are inserting), and make
	# the operation unlogged
	$sth->syb_ct_data_info('CS_SET', 1, {total_txtlen => length($long_text), log_on_update => 0});
	# now transfer the data (in a single chunk, this time)
	$sth->syb_ct_send_data($long_text, length($long_text));
	# commit the operation
	$sth->syb_ct_finish_send();
}