LibXML and DTD"s

Hello, all. How can I access DTD information using LibXML? I want to
find anything that looks like this...

mydomain.com/ns/ese">

....and get the namespace prefix ("Ese") and URI ("http://mydomain.com/
ns/ese"). Of course, I can parse through the DTD as text with
regexps, but the DTD isn't contained in a single file (there are
external entities nested in external entities, etc.) so this will be
difficult.

I've checked XML::LibXML::Dtd and the XML::LibXML::Document methods
externalSubset and internalSubset, but could not figure out how to
apply them...

Any help would be appreciated. Thanks.