Object sub-classing advice sought

waldo has asked for the wisdom of the Perl Monks concerning the following question:

A while back I stumbled across Tim Bunce's Treemap blog and thought I'd have a go at producing an SVG output module based on the Treemap module.

I want to produce a version that drills down through the data revealing more detail at each level. To do this I need to produce an hierarchical SVG document. But the existing Treemap module only passes on drawing data (coordinates, colour and text) when invoking the output objects methods.

Is sub-classing the Treemap object and adding the additional data in the method invocations the only way?
Am I missing an easier solution?
What would I call such a module? (Treemap::Drilldown/Treemap::Hierarchical ...)
For the output class I've used Moose, because part of the rationale of doing this is to get experience with Moose (and Javascript and SVG). Is it a good idea to have this dependency in the final version (the original module is 5+ years old so doesn't use it)?

Example of use below:

Input data:

<children name="main" size="6" colour="antiquewhite">
   <children name="Treemap" size="4" colour="#FF0000">
     <children name="xmlify" size="2" colour="#00FF00" />
     <children name="save01" size="2" colour="#00FF00" link="save01.ht
+ml" />
   </children>
   <children name="Treemap::Output::SVG" size="6" colour="#FFFF00" >
     <children name="rect" size="1" colour="#00FFFF" />
     <children name="text01" size="4" colour="whitesmoke">
      <children name="text02" size="2" colour="#00FF00" >
       <children name="text02_01" size="1" colour="#F0F0F0" />
       <children name="text02_02" size="1" colour="#F0F0F0" />
      </children>
      <children name="text03" size="1" colour="#00FF00" /> 
      <children name="text04" size="1" colour="cyan" />
     </children>
     <children name="save02" size="1" colour="gray" />
   </children> 
</children>
[download]

Creating an SVG output file:

use Treemap;
use Treemap::Input::XML;
use Treemap::Output::SVG;

# read the XML input file
my $in = Treemap::Input::XML->new();
$in->load( "inputfile.xml" );


my $out = Treemap::Output::SVG->new();

my $treemap = Treemap->new( INPUT=>$in, OUTPUT=>$out);
# create a treemap in SVG using the XML input file provided
$treemap->map();

# save the results to a file
$out->save( "outputfile.svg" );
[download]

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