I have a lot of troubles with Tk and internationalization on Linux and Windows with Perl. In Windows I use StrawberryPerl.
1. For Unix you must use Unicode and all must be normal, but for filenames you will have problems. Tk use as standard iso-8859 codepage(if I remember this number) for filenames. And if you need use UTF-8 then you must get problems. Filedialog from Tk work wrong with UTF-8 filenames. This was my bigest problem with Tk. It show in dialog utf-8 filenames as ???. I must create my own filedialog with UTF-8.
2. All methods from Tk work with latin codepage and can't open utf-8 filenames(method Photo as example). For this methods I create subroutine for translate name to latinic filename and use in Photo latinic filename.
3. In Windows filename codepage use ONLY national codepage. For example: for cyrylic filenames it must be cp1251(if Windows MUI is cyrylic)...
4. For data in filenames I use utf-8 and you must keep in mind this and encode data if this need. Also Windows use CrLf ending of line. In Unix only Cr.

Mostly my questions on PerlMonks was about codepages in Tk and others about internationalizations. You can see my profile and read all about this theme in my feeds...