use Data::Dumper;

package Package1;

sub new
{
  my($class)  = shift;
  my(%params) = @_;

  bless {
        "CONTENT"    => $params{"content"},
  }, $class;
}

sub shout
{
  my $self = shift;
  print "SHOUT\n";
}

package Package2;

@ISA = (Packerl1);

sub new
{
  my($class)  = shift;
  my(%params) = @_;
  my($self) = Package1->new(@_);
  $self->{"ADDITIONAL_CONTENT"} = $params{"additional_content"};
  return(bless($self,$class));
}

sub shout
{
  my($self) = shift;
  print "SCREAM\n";
}

package main;

$p1 = Package1->new("content" => "this is the content");
$p2 = Package2->new("content" => 'less content', "additional_content" => 'more_content');

$p1->shout;
$p2->shout; 

print Dumper $p1;
print Dumper $p2;