plperl & large objects

Hello!
I wrote the function in plperlu. I know it works (I ran in from
file). This code is from my function:
$oid = $dbh->func($dbh->{pg_INV_WRITE}, "lo_creat");
$lobj_fd = $dbh->func($oid, $dbh->{pg_INV_WRITE}, 'lo_open');
$nbytes = $dbh->func($lobj_fd, $objxml, $xmllength, "lo_write");
$lobj_fd = $dbh->func($lobj_fd, "lo_close");
When function runs postgres returns different reasons. Sometimes
it says "There is no large object with oid: ..." Sometimes it says
that allocated memory is not enough. Has anyone the same
problem?
Please help me:)

Best regards,
Peter