package Data;

sub new { ... }
sub other { ... }

#no "process" package


package My::ProcessA;

BEGIN { #reverse inheritence code into Data }

sub processA {
   my ( $data, @opts ) = @_;  #$data is a Data instance\
   ...
   return new Data( $stuff );
}

package My::ProcessB;

BEGIN { #reverse inheritence code into Data }

sub processB {
   my ( $data, @opts ) = @_;  #$data is a Data instance
   ...
   return new Data( $stuff );
}


# In code:
use Data;
use My::ProcessA;   (Data::processA appears, magically!)
use My::ProcessB;   (Data::processB appears, magically!) 

my $data = new Data ( $data_from_file );

# Now possible, woohoo!
my $processed = $data
                    ->processA( @Aopts )
                    ->processB( @Bopts );

##</code><code>##

my $newdata = $data->processA( @opts ); #scalar
              $data->processA( @opts ); #void