package Foo;

sub new{
	my ($class, filespec) = @_;
	# check for existance, other init stuff
	return bless {file=>$filespec }, $class;
}

sub sort{ 
	$self = shift;
	system( 'sort', $self->$filespec, '>', "$self->filespec.sorted" );
	return $self->new( "$self->$filespec.sorted" );
}

sub munge{ 
	$self = shift;
	system( 'munge', $self->$filespec, '>', "$self->filespec.munged" );
	return $self->new( "$self->$filespec.munged" );
}

1;
package main;
# Start with a object created  by the user.
my $data = Foo->new( 'datafile' );;

# Munge it two different ways and get two seperate objects back representing the two new states
my $sorted = $data->sort();
my $munged = $data->munged();

# Further processing on the new state is invoked directly on the new object
my $sorted'n'munged = $sorted->munge();
my $munged'n'sorted = $munged->sort();

# Or even pipeline them
my $sorted'n'munged'n'sorted_again = $data->sort()->munge()->sort();