This is a nice alternative, pokki, I really don't need an ORM for my current purpose. What I am trying to achieve is getting the information about constraints in a uniform way for as many DBMSs as possible, and it has been suggested that I try DBIx::Class::Schema::Loader. As I can see, SQL::Translator supports all of the DBMSs I wanted to support, so I am fine with SQL::Translator, too.
What I could not get from the documentation is in which form the dump of the database structure which is passed as second parameter to parse() is expected (for each supported DBMS). Do you know the expected format?