I made a proper module and fixed most problems: it constructs a Parrot interpreter object, and uses it throughout the program - so that it is now much faster, and we can have global Parrot variables. You can also create and kill additional interpreters at will. It's now using Parrot-calling conventions, as suggested.

The current version is here: http://www.ipct.pucrs.br/flavio/perl/Inline-Parrot-0.04.tar.gz

Thanks for all the people who contributed with suggestions!