AnyEvent recursive blocking wait error

evtest.pl

use AnyEvent;


my $cv = AE::cv;

my $t = AE::timer 2,0, sub{
    my $cv2 = AE::cv;
    my $cnt = 10;
    my $tot = 0;
    foreach(1..10){
        my $idx = $_;
        my $tt; $tt = AE::timer 1,0,sub{
            print "$idx\n";
            $tot+=$idx;
            $cnt--;
            $cv2->send unless $cnt;
        }
    }
    $cv2->recv;
    print "tot: $tot\n";

};



$cv->recv;
print "DONE\n";
# EV: error in callback (ignoring): AnyEvent::CondVar: recursive blocking wait attempted at ev.pl line 19

I had this error today, can you elaborate a bit more on what's happening there?