I have a tcp server which is accepting data from gprs clients and one client from localhost, which is serving command to other clients.
The clients are always connected to the server, except when is some network outage or other gprs disconnections. Then, clients reconnects to the server

And there is my problem: Old threads remains connected to the server and I need to get rid of them!
Obviously I'm a novice with Perl, so I posted my tcp server code to get also some opinions for improvement.

#!/usr/bin/perl
use warnings;
use strict;
use IO::Socket;
use threads;
use threads::shared;

$|++;
print "$$ Server started\n";;  # do a "top -p -H $$" to monitor server
+ threads

my $buf2;
my $SyncID;
my $SyncHeader;
my $UnitID;
our @clients : shared;
@clients = ();
our $k;
our $m;
our $n;
our $p;
our $dup=0;
our $sel_cli2;

my @Mdevices;

my $ref;
my $peerC = 1;
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my $server = new IO::Socket::INET(
    Timeout   => 500,
    Proto     => "tcp",
    LocalPort => 8000,
    Reuse     => 1,
    Listen    => 5

);

my $num_of_client = -1;

while (1) {
    my $client;
    do {
        $client = $server->accept;
    } until ( defined($client) );


        my $peerhost = $client->peerhost();
        $peerC = $peerhost;

    if ($peerC ne '127.0.0.1')
{
        my $template = 'vvV';
        read $client, my $sync_packet,8
        or die "Couldn't read from client: $!";
($SyncHeader,$SyncID,$UnitID) = unpack $template, $sync_packet;

    print "accepted a client $client, $UnitID, $peerhost, id = ", ++$n
+um_of_client, "\n";

} else {
        $UnitID = 888;

print "accepted a client $client, $peerhost, id = ", ++$num_of_client,
+ "\n";

}
    my $fileno = fileno $client;
    push (@clients, $fileno);


        for ($k=0; $k<=$#Mdevices; $k++)
            {
                   if ($Mdevices[$k][0] eq $UnitID) # searching existi
+ng UnitID in Array
                        {
                                $dup =1;
                                print "Duplicate found $Mdevices[$k][0
+] |";

                                $Mdevices[$k][1] = $fileno; # update e
+xisting UnitID with new fileno
                        }
                }
                                if ($dup eq 1)
                                {
                                        print "NO changes |";
                                        $dup = 0;
                                } else {

                                                for ($n=0; $n<=$#Mdevi
+ces; $n++) # chech if exist some entry with old fileno, should be del
+eted
                                                {
                                                        if ($Mdevices[
+$n][1] eq $fileno)
                                                        {
                                                                print 
+"deleting |";
                                                                $Mdevi
+ces[$n][1] = 0; # set old entry's fileno to 0 to not interfere.
                                                        }
                                                }

                                push (@Mdevices, [$UnitID, $fileno]); 
+# add new device with fileno to array

                        }
use Data::Dumper;
print Dumper(\@Mdevices);


    #spawn  a thread here for each client
    my $thr = threads->new( \&processit, $client, $fileno, $peerhost )
+->detach();

}
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sub processit {
     my ($lclient,$lfileno,$lpeer) = @_; #local client

        my $sel_cli_id = $num_of_client;

     if($lclient->connected){

          while(<$lclient>)
        {

                if ($peerC eq '127.0.0.1') # tcp client from localhost
+ is used just to send commands to other connected clients
                {
                        my(@comm) = split(/:/, $_);
                        my $sel_clix = $comm[0];
                        my $commandC = $comm[1];

                for ($p=0; $p<=$#Mdevices; $p++)
                {
                        if ($Mdevices[$p][0] eq $sel_clix)
                        {
                                $sel_cli2 = $Mdevices[$p][1];
                        }

                }

                        foreach my $fn ($sel_cli2)

                        {
                                if ($sel_cli2)
                                {
                                        open my $fh, ">&=$fn" or warn 
+$! and die;
                                        print "\n $lclient $sel_cli2 C
+ommand sent to: $sel_clix Command: $commandC";
                                        print $fh  "$commandC\n"

                                } else {

                                        print "\n $lclient Device: $se
+l_clix NOT avaiable to receive command\n";

                                }
                        }

                } else {

                print "COMMAND RESPONCE: $_";
}
          }
    }
                  #close filehandle before detached thread dies out
                  close( $lclient);
                  #remove multi-echo-clients from echo list
                  @clients = grep {$_ !~ $lfileno} @clients;

}
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