Perl) Paul Hoffman's test tool is written in Perl, and free. It is not a ready-to-use, shrinkwrapped library (for instance, there are hardcoded paths in the code). Requires Perl >= 5.8. <URL:http://www.imc.org/idna/>
For Perl, we'll try to develop an XS interface, allowing to use GNU libidn, written in C.
--Paul Hoffman, Director --Internet Mail Consortium