my $loop = AnyEvent->condvar;
my $a = 0;

sub heartbeat {
    open( $fh, '>>', $msg_log );
        print $fh "looping $a\n";
    close $fh;
};

AnyEvent->timer( interval => 5, cb => \&heartbeat );
$loop->recv;
exit 0;

##</code><code>##

$iocv->cb( \&on_io );

sub on_io {
    open( $fh, '>>', $msg_log );
        print $fh "loop data: $data\n";
    close $fh;
    undef( $iocv );
    $iocv = AnyEvent->condvar;
    $iocv->cb( \&on_io );
};