# 
$c = {
  'foo.com' => {
     dbname => 'foo',
     dbuser => 'foo',
  },
  'bar.com' => {
     dbname => 'bar',
     dbuser => 'bar',
  }
};

sub param {
  my $param = shift;
  # get a request instance
  my $r = Apache::Request->instance();
  # get the hostname
  my $host = $r->hostname();
  return $c->{$host}->{$param};
}