package Animal; 

sub new { return bless {},"Animal"; } 
sub speak { };

1; 

package Animal::Dog;
use Animal;
our @ISA = qw/ Animal /;

sub new { return bless {},"Animal::Dog"; } 
sub speak { print "Woof!\n"; } 

1;

package Animal::Cat;
use Animal;
our @ISA= qw/ Animal /;

sub new { reutrn bless {},"Animal::Cat"; } 
sub speak { print "Meow!\n"; } 

1; 

-- ad nauseum --

##</code><code>##

package Report;

sub new {
    shift;
    my $type= shift; 
    my $self = { 
           format => "html",
           destination => undef 
    };
    my $token = ( 
         $type == 1 ? "::HighLevel" : "::Status" );
    bless $self,"Report" . $token;
} 

sub emit {
    my $self = shift; 
    if { $self->{destination} ) { 
       if ( $self->{format} eq 'html' ) { 
           print $self->{destination} $self->as_html();
       } else { 
           print $self->{destination} $self->as_text();
       }
    } else { 
        if ( $self -> {format} eq 'html' ) { 
           print $self->as_html();
        } else { 
           print $self->as_text(); 
        } 
    } 
} 

sub set_format { 
     my ($self,$format} = @_;
     $self->{format} = $format;
} 

sub set_destination {
     my ($self,$destination) =@_;
     $self->{destination} = $destination;
}

sub generate { 
}

;

package Report::HighLevel;
use Report;
our @ISA=qw/ Report /;

sub generate { 
   my $self = shift;

      # report generation logic here...
} 

sub as_html{
# HTML generation code here. 
}

sub as_text {
# text generation code here. 
}

1; 


##</code><code>##

my $report1 = new Report(1);  # gets Report::HighLevel
my $report2 = new Report(0);  # gets Report::Status

$report1->generate();
$report2->generate();