Read the documentation of your switch, and maybe a good book about TCP.

I highly doubt that you can influence the network traffic from the mirror port, because the mirror port just gets a copy of all data, but cannot take part in the network communication.

i mean to implement pass by filtering like http://smoothwallweb.s3.amazonaws.com/WhitePaper/PassBy%20White%20Paper%20-%2006-2011.pdf

Have you read that paper? Even that paper tells you that what you want does not work, and also even tells you why. Even with pretty pictures. And it is a paper telling its readers that "pass by" filtering is a thing of the past.

I suggest you learn about the topic, like I already suggested, two times.

i am able to view the all urls but dont understand how to block it.

Where?

proxy?

All users are connected to one port switch this port is mirror where i have connected single machine with freebsd operating system.I am using Sniffer::HTTP module to catch the url.i want to block xyz.com for all users . i dont know how i can do it please find the following codes for your reference

#!/usr/bin/perl
use strict;
use Net::Pcap;
use Sniffer::HTTP;
use Net::RawIP;
my $VERBOSE = 0;
  


my $sniffer = Sniffer::HTTP->new(
callbacks => {
request  => sub { my ($req,$conn) = @_; 
my $src = $conn->tcp_connection->src_host;
my $sport = $conn->tcp_connection->src_port;
my $dst = $conn->tcp_connection->dest_host;
my $dport = $conn->tcp_connection->dest_port;
my $myurl = $req->uri;



if ( $myurl =~ "http://xyz.com" )

{


system("/usr/bin/perl /myscripts/socket3.pl $dst $dport $src $sport");


}


print "Request: $src:$sport -> $dst:$dport -> $myurl \n";


}
},
);
$sniffer->run('alc0'); # uses the "best" default device
[download]

code of /usr/bin/perl /myscripts/socket3.pl

use Net::RawIP;

$src_host = $ARGV[0]; # The source IP/Hostname
$src_port = $ARGV[1]; # The Source Port
$dst_host = $ARGV[2]; # The Destination IP/Hostname
$dst_port = $ARGV[3]; # The Destination Port.


  $n = Net::RawIP->new({
                        ip  => {
                                saddr => "$src_host" ,
                                daddr => "$dst_host",
                               },
                        tcp => {
                                source => "$src_port",
                                dest   => "$dst_port",
                                rst    => 1,
                               },
                       });
  $n->send;
  $n->ethnew("alc0");
  $n->ethset(source => "$src_host", dest => "dst_host" );    
  $n->ethsend;
[download]

Please learn about TCP, and learn about what Sniffer::HTTP does.

There is no way to modify the network connection or data using Sniffer::HTTP.

Have you looked at the HTTP proxy modules on CPAN?