Actually XML::Parser reads the DTD, and in 2.28 and later gives you quite a bit of information about it, so you could use it to generate a tree, that you could then walk (choosing at random when faced with an alternative, or just generate _all_ alternatives and choose the shortest or some other more sophisticated heuristic) to generate a valid instance.

An alternative to generating atree would be to generate a Parse::RecDescent grammar and then I think you can use a feature of Parse::RecDescent that let's you generate a valid instance conformant to the grammar.

I did that a long time ago, in C, to generate test documents for an SGML project I was working on and it worked fine, except that it was not based directly on the DTD. You usually need more information than a DTD will give you (what kind of text is expected, what kind of ID/REFID links do you want to generate etc...)