sub new {
  my ($class, @args) = @_;

  my $this;
  unless (defined @args) {
    $this = $class->SUPER::new(); # call zero-arg ctor
    return bless($this, $class); # rebless to our class
  } else {
    # do argument checking to figure out what ought to go
    # to the superclass ctor and what needs to be initialized here.
    $this = $class->SUPER::new(@some_args);
    # then initialize the parts of the object that are unique to this class
    return bless($this, $class); # rebless to our class
  }

##</code><code>##

sub new {
  my ($class, %args) = @_;

  my $this = $class->SUPER::new(%args);
  # Do additional processing on the args, e.g ...
  $$this{foo} = $args{foo};
  return bless($this, $class); # rebless to our class
}

##</code><code>##

package SomeSuperclass;
sub new {
     my $class = shift();
     my $this = {};
     bless($this, $class);
     $this->_init(@_);
     return $this;
}

##</code><code>##

package SomeSubclass;
use base SomeSuperclass;

sub _init {
  my ($this, $foo, $bar, $baz) = @_;
  $this->SUPER::_init($bar, $baz);
  $$this{foo} = $foo;
}