libxml-dtdparser-perl binary package in Ubuntu Xenial amd64

 XML::DTDParser parses a DTD file and creates a data structure containing info
 about all tags, their allowed parameters, children, parents, optionality etc.
 .
 The module should be able to parse just about anything, but it
 intentionaly looses some information. Eg. if the DTD specifies that a tag
 should contain either CHILD1 or CHILD2 you only get that CHILD1 and CHILD2
 are optional. That is the DTD contains
 .
 <!ELEMENT FOO (BAR|BAZ)> the result will be the same is if it contained
 .
 <!ELEMENT FOO (BAR?,BAZ?)>
 .
 You get the original unparsed parameter list as well so if you need this
 information you may parse it yourself.

Source package