sub credentials
{
    my $self = shift;
    my $netloc = lc(shift);
    my $realm = shift || "";
    my $old = $self->{basic_authentication}{$netloc}{$realm};
    if (@_) {
        $self->{basic_authentication}{$netloc}{$realm} = [@_];
    }
    return unless $old;
    return @$old if wantarray;
    return join(":", @$old);
}