This module adds XPath-style matching to your object trees. This means that
you can find nodes using an XPath-esque query with 'match()' from anywhere
in the tree. Also, the '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.

*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.