While Perl/Tk now seems to get along reasonably well with unicode (try installing and watch what happens during "make test"...), alas it will probably never be able to tackle bidirectional text, let alone the proper ligatures for Arabic script. (If someone knows this to be false, please tell me more about that.)

I have yet to try the other GUI library API's (Gtk and Qt), but I know the Perl modules exist for these, and I know that people have used these libraries to create reasonably successful bidi/Arabic interfaces. (And if you can do that, you can do just about anything.)