ct_param() failed! at /tmp/xx.pl line 33.
DBD::Sybase::st execute failed: OpenClient message: LAYER = (1) ORIGIN = (1) SEVERITY = (1) NUMBER = (16)
Message String: ct_param(): user api layer: external error:
    This routine cannot be called while results are pending for a command that has been sent to the server.
DBD::Sybase::st execute failed: OpenClient message: LAYER = (1) ORIGIN = (1) SEVERITY = (1) NUMBER = (16)
Message String: ct_param(): user api layer: external error:
    This routine cannot be called while results are pending for a command that has been sent to the server.
##</code><code>##

#!/usr/bin/perl

use strict;
use warnings;

use DBI;

my $dbh1 = DBI->connect("dbi:Sybase:server=server1;database=database1", 'user1', 'passwd1');
my $dbh2 = DBI->connect("dbi:Sybase:server=server2;database=database2", 'user2', 'passwd2');

my $sth1 = $dbh1->prepare("select * from table1");
my $sth2 = $dbh2->prepare("select * from table2 where primkey = ?");

$sth1->execute;

#---- iterate through table1, check in table2
while (my @row1 = $sth1->fetchrow_array) {

  $sth2->execute($row1[0]);                               # this is line 33
  my @row2 = $sth2->fetchrow_array;
}