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;
  }
}

##</code><code>##

package URL::Storable;
{ 
  our @ISA=qw(URL);
  sub new {
    my $package=shift;
    my $argsp = $_[0];
    # setting a "per-class" var, not per-instance
    if (exists $argsp->{save_prefix}) {
      $save_prefix=$argsp->{save_prefix};
    }
    my $this=new URL(@_);
      # (process this packages args....)
    bless $this, $package;  #bless and return
  }
}