package App::Backend;

use App::Config;
use base "App::Backend::App::$Config::Backend_Type";

sub shared_method_1 { 
    my $self = shift; 
    #....
}

# ... the rest of the module...
1;


##</code><code>##

 
 sub type { 

   my $self = shift; 
   return 'SQL'; 
}


##</code><code>##

 
 sub type { 

   my $self = shift; 
   return 'PlainText'; 
}


##</code><code>##

#!/usr/bin/perl 
use Test::More qw(no_plan); 

for(qw(PlainText SQL){ 
    require App:Config; 
    $App::Config::Backend_Type = $_;

    require App::Backend; 

    ok($App::Config::Backend_Type eq $_); 
    my $backend = App::Backend; 
    ok($backend->type eq $_); # Wrong! 

}