package Employee;
sub new {
  my ($class,$fname,$lname) = @_;
  die if $class eq 'Employee';
  bless { FNAME => $fname, LNAME => $lname }, $class;
}

package Employee::Boss;
@ISA = qw( Employee );
sub new {
  my ($class,$fname,$lname) = @_;
  my $self = $class->SUPER::new($fname,$lname);
  $self->{PAY} = 1_000_000;
  bless $self, $class;
}

# and so on...