Data::stag is for manipulating data as hierarchical tag/value pairs (structured tags or simple tree aggreggates). these datastructures can be represented as nested arrays, which have the advantage of being native to perl. a simple example is shown below:

[ person=> [ [ family_name => $family_name ],
[ given_name => $given_name ],
[ phone_no => $phone_no ] ] ],
data::stag uses a subset of xml for import and export. this means the module can also be used as a general xml parser/writer (with certain caveats).