package Old;

sub new {
   my ($class,@arg) = @_;
   my $self = {};
   return bless $self,$class;
}

# pretend these return HTML pages generated via CGI.pm
sub index { "CGI.pm index page" }
sub page1 { "CGI.pm page1" }
sub page2 { "CGI.pm page2" }
sub page3 { "CGI.pm page3" }

1;

##</code><code>##

package New;

sub new {
   my ($class,@arg) = @_;
   my $self = {};
   return bless $self,$class;
}

# pretend these return HTML pages generated via HTML::Template
sub index { "H::T index page" }
sub page2 { "H::T page2" }       # page 2 was easier than 1 ;)

1;

##</code><code>##

package Interface;

use Old;
use New;

sub new {
   my ($class,@arg) = @_;
   my $self = {};
   return bless $self,$class;
}

sub index { return New->new()->index }
sub page1 { return Old->new()->page1 }
sub page2 { return New->new()->page2 }
sub page3 { return Old->new()->page3 }

1;

##</code><code>##

use strict;
use warnings;
use Interface;

my $obj = Interface->new;

print $_,$/ for map $obj->$_, qw(index page1 page2 page3);

##</code><code>##

package Interface;

use Old;
use New;
use Carp;

sub new {
   my ($class,@arg) = @_;
   my $self = {};
   return bless $self,$class;
}

my %new = map {$_ => 1} qw(index page3 page2);
sub AUTOLOAD {
   my $self = shift;
   my $name = $AUTOLOAD;
   $name =~ s/.*://;   # strip fully-qualified portion

   #TODO: method name validation!

   return $new{$name}
      ? eval "New->new->$name"
      : eval "Old->new->$name"
   ;
}

sub DESTROY {}  # good practice - prevents unecessary call to AUTOLOAD

1;