{
   package ClassA;
   ...
   sub new {
      ...
      my $self = bless({}, $class);
      $self->{...} = ...;
      return $self;
   }
   ...
}

{
   package ClassB;
   our @ISA = 'ClassA';
   sub new {
      ...
      my $self = $class->SUPER::new();
      $self->{...} = ...;
      return $self;
   }
   ...
}

{
   package ClassC;
   our @ISA = 'ClassB';
   sub new {
      ...
      my $self = $class->SUPER::new();
      $self->{...} = ...;
      return $self;
   }
   ...
}