package URL;
{...
  sub new {
    my $package=shift;
    my $argsp = $_[0];
    my $up= {
      host => '',
      path => '',
    };
    foreach (keys %$up, @arg_aliases) {
      $up->{$compose_argmap{_tl( $_)}}=$argsp->{$_} if exists $argsp->{$_};
    }
    bless $up, $package;
  }
}