Stomp client hang after a long time pending

i have a program which use stomp to receive messages from activemq,
when i start it and wait for several minutes before close it, everything is ok.
but if i wait for one hour, for example, when i close it, then i find from the management page, the two consumers are still there.
and if i restart the program with these tow hanging consumers, then i could not receive any message.
i do not know whether it is a bug or just my program problem, sorry for disturb you here for an analyse, please.
here is my program:
#!/usr/bin/perl -w
use strict;
use Switch;
use Time::HiRes qw(usleep ualarm gettimeofday tv_interval);

use Net::Stomp;

use Term::ANSIColor;
#for multithread
use threads;
use threads::shared;

#for ActiveMQ connection
my $aq_host = "10.255.1.130";
my $aq_port = '61613';
my $sSender;
my $sReceiver;
my $aReceiver;

my $queue1 = "queue1";
my $queue2 = "queue2";

my $running : shared = 1;

my $thread_th1;
my $thread_th2;

sub cleanup()
{
print colored ("\n.STOP received! \n", 'red');
$running=0;
print ".Stopping Thread1 ...... ";
my $r1 = $thread_th1->join();
print colored ("$r1\n", 'green');

print ".Stopping Thread2 ...... ";
my $r2 = $thread_th2->join();
print colored ("$r2\n", 'green');

print ".Disconnecting ActiveMQ connector ...... ";
$sReceiver->disconnect();
$aReceiver->disconnect();
print colored ("OK\n", 'green');

print "\n";
print colored ("ALL Nicely Stopped, see you!\n\n", 'yellow');
}

sub th1()
{
$sReceiver->subscribe(

{ destination => "/queue/$queue1", 'ack' => 'client', 'activemq.prefetchSize' => 1}

);
while($running){

if ($sReceiver->can_read(

{timeout=>'1'}))
{
my $frame = $sReceiver->receive_frame;
my $body = $frame->body;

#print "get message from queue 1: $body \n";
ptMsg($body);
#Ack msg for deleting after the procedure
$sReceiver->ack({ frame => $frame});
}
}

$sReceiver->unsubscribe({ destination => "/queue/$queue1"});
return "OK";
}

sub th2()
{
$aReceiver->subscribe({ destination => "/queue/$queue2", 'ack' => 'client', 'activemq.prefetchSize' => 1});
while($running)
{
#get one message from queue
if ($aReceiver->can_read({timeout=>'1'}

))
{
my $frame = $aReceiver->receive_frame;
my $body = $frame->body;
#print "get message from queue 2: $body";
ptMsg($body);
$aReceiver->ack(

{ frame => $frame}

);
}
}
#when received cleanup message
$aReceiver->unsubscribe(

{ destination => "/queue/$queue2"}

);
return "OK";
}

sub ptMsg
{
my $msg = shift;
print "received message $msg \n";
}
#################################################################

1. main function start
   #################################################################

print ".Creating ActiveMQ connector ...... ";
$sReceiver = Net::Stomp->new(

{ hostname => $aq_host, port => $aq_port});
$sReceiver->connect();
$aReceiver = Net::Stomp->new({ hostname => $aq_host, port => $aq_port}

);
$aReceiver->connect();
print colored ("OK\n",'green');

$SIG

{INT}

= "cleanup";

print ".Starting Thread1 ...... ";
$thread_th1 = threads->create(\&th1);
print colored ("OK\n", 'green');

print ".Starting Thread2 ...... ";
$thread_th2 = threads->create(\&th2);
print colored ("OK\n", 'green');

#main process waiting for signal clean
print colored ("->running ......\n", 'green');
print "\n";

while ($running) {
usleep(5000000);
}