#!/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;
}