sub _waitpid_blocking {
    my $self = shift;
 
    # pseudo-blocking
    if( my $sleep_period = $self->{waitpid_blocking_sleep} ) {
        while() {
            my $pid = $self->_waitpid_non_blocking;
            return $pid if $pid;
 
            sleep $sleep_period; # should be line 782
        }
    }
 
    return waitpid -1, 0;
}