sub new {
  my $class = shift;
  return bless {}, $class;
}

sub new_with_logger {
  my $proto = shift;
  my $logger = shift;
  return $proto->new->set_logger($logger);
}

sub set_logger {
  my $self = shift;
  my $logger = shift;
  # If you insist...
  eval { $logger->isa('Logger') } or 
    croak "New logger must be an instance of Logger class"
  $self->{logger} = $logger;
  return $self;
}