use strict;
use warnings;
use LWP::UserAgent;

my $ua = LWP::UserAgent->new(keep_alive => 1);
my $url = "http://example.com/myUrl";
my $token = undef;

while(1)
{
	my $res = $ua->get($url, 'Start-From' => $token // "", 'X-AcceptDeltaUpdates' => 'true');
	$token = $res->headers->{'token'} if ($res->headers->{'token'});
	print $res->decoded_content if ($res->is_success);
	sleep 4;
}