In your node class, use Class::XPath:

  # generate xpath() and match() using Class::XPath
  use Class::XPath

     get_name => 'name',        # get the node name with the 'name' method

     get_parent => 'parent',    # get parent with the 'parent' method

     get_root   => \&get_root,  # call get_root($node) to get the root

     get_children => 'kids',    # get children with the 'kids' method

     get_attr_names => 'param', # get names and values of attributes
     get_attr_value => 'param', # from param
     
     get_content    => 'data',  # get content from the 'data' method
     
     ;

Now your objects support XPath-esque matching:

  # find all pages, anywhere in the tree
  @nodes = $node->match('//page');

  # returns an XPath like "/page[1]/paragraph[2]"
  $xpath = $node->xpath();

=head1 DESCRIPTION

This module adds XPath-style matching to your object trees.  This
means that you can find nodes using an XPath-esque query with
C<match()> from anywhere in the tree.  Also, the C<xpath()> method
returns a unique path to a given node which can be used as an
identifier.

To use this module you must already have an OO implementation of a
tree.  The tree must be a true tree - all nodes have a single parent
and the tree must have a single root node.  Also, the order of
children within a node must be stable.

B<NOTE:> This module is not yet a complete XPath implementation.  Over
time I expect the subset of XPath supported to grow.  See the SYNTAX
documentation for details on the current level of support.

=head1 USAGE

This module is used by providing it with information about how your
class works.  Class::XPath uses this information to build the
C<match()> and C<xpath()> methods for your class.  The parameters
passed to 'use Class::XPath' may be set with strings, indicating
method names, or subroutine references.  They are:

=over

=item get_name (required)

Returns the name of this node.  This will be used as the element name
when evaluating an XPath match.  The value returned must matches
/^[\w:]+$/.

=item get_parent (required)

Returns the parent of this node.  The root node must return undef from
the get_parent method.

=item get_children (required)

Returns a list of child nodes, in order.

=item get_attr_names (required)

Returns a list of available attribute names.  The values returned must
match /^[\w:]+$/).

=item get_attr_value (required)

Called with a single parameter, the name of the attribute.  Returns
the value associated with that attribute.  The value returned must be
C<undef> if no value exists for the attribute.

=item get_content (required)

Returns the contents of the node.  In XML this is text between start
and end tags.

=item get_root (required)

Returns the root node of this tree.

=item call_match (optional)

Set this to the name of the C<match()> method to generate.  Defaults
to 'match'.

=item call_xpath (optional)

Set this to the name of the C<xpath()> method to generate.  Defaults
to 'xpath'.