# host_base set from 'host' when host_mask is set;     Example:
  # if host_base==www.first.host & hostmask gets us "first.host"
  # i.e. hostmask would be only looking at the last 2 domainname-parts
  # in future matches, a host would first have the mask applied 
  # (masking off a 3rd level sub-domain part), then match against
  # first_host .. resulting in a match if 
  # that's subtracted from future relative saved paths.
  
  our ($pkg_host_mask, $pkg_host_base);
  our $items_from_cache=0;
  our $Cache_Control;


  sub host_mask (;$) { my $p = shift;
    return $pkg_host_mask if $pkg_host_mask; 
    $pkg_host_mask = $_[0] if @_;
    $pkg_host_mask
  }

  sub host_base(;$) {
    my $p = shift;
    my $reset=1 if @_ && EhV shift, reset; 
    return $pkg_host_base if $pkg_host_base && ! $reset;
    if (@_) { $pkg_host_base=$_[0]; }
    elsif ($p->host && $pkg_host_mask) {
      P "pkg_host_mask=%s, host=%s", $pkg_host_mask:
      $pkg_host_base = ($p->host =~ m{($pkg_host_mask)}) [0];
    }
    return $pkg_host_base;
  }


  # returns empty-string if same site, or sitename+dir_sep if not;
  # caches result in {host_path}
  
  sub host_path {
    my $p = $_[0] or return undef;

    my ($host_base, $host_mask) = ($p->host_base, $p->host_mask);
    $host_base && $host_mask && $p->host or 
    die P "Can't produce host_path w/o host_base( host(%s) & mask(%s) )",
            $p->host, $host_mask.
    
    ( ($p->host =~ m{$host_mask/})[0] eq $host_base ) ? '' : $p->host;
  }