Call an oracle SP and using bind variables

I need to call an oracle stored procedure and pass parameter to that procedure from perl, using bind variables. I have written some code.
But it is giving the error
Can't bind unknown placeholder ':binlocator' at testt.pl line 42

Note: In that one of the parameter is of type Blob,

The code I had written is


use strict;
use DBI;
my $dbh;
my $sth;
my $dsn;
my $stmt;
my $sth_output;
my @row;
# my  $bin_locator;
$dsn = "DBI:ODBC:dsn";
$dbh = DBI->connect($dsn, "****", "****") || die "Database connection not made: $DBI::errstr";
$stmt = "INSERT INTO temp (n1,n2) VALUES (1, EMPTY_BLOB())";
$dbh->do($stmt);

 $sth = $dbh->prepare( <<" SQL", { ora_auto_lob => 0 } );
 SELECT N2  FROM temp WHERE n1 = 1 FOR UPDATE
 SQL
 $sth->execute();
#my ($bin_locator) = $sth->fetchrow_array();
@row = $sth->fetchrow_array;
# print "Row: @row\n";

my ($bin_locator) = $row[0];
#print "-->Row_0 $row[0] <--";
 $sth->finish();



#3) Open Document files. Insert in Chunks of 2000 bytes

open BIN_FH, "C:\\Temp\\ust\\data.txt" or die;
 my $chunk_size = 2000; # Arbitrary chunk size

 my $buffer = '';
 while ( read( BIN_FH, $buffer, $chunk_size ) ) {

#
#  The error is happening here
#

 $sth_output = $dbh-> prepare("BEGIN DBMS_LOB.WRITEAPPEND(:binlocator, 2000, :buffertemp ); END;");
 $sth_output->bind_param(":binlocator", $bin_locator);
 $sth_output->bind_param(":buffertemp",$buffer,2000);
 $sth_output-->execute();

 
 $sth_output->execute();
 
 }


How can i do that?
Any help greatly appreciated ..