I'd like to have a sandbox in Perl, where unicode were treated naturally.

Unicode is largely treated naturally in Perl (at least since 5.8.1).

Agreed. But to get "sand" (characters) to this box is painful. AFAIU, we have already today in Perl all (at least most) needed pieces to control bits coming from outside world. (And let us expect, that OS is perfect, because it is out of our control.) Those pieces are OUT THERE, but not together.

I can use them together, but it took too much time to put the puzzle together. I am still not sure, are they now correctly on place and whole thing is too fragile. If in Perl development something changes, i may got broken code as well. For example: for me was great solution to use -C on first line, but from 5.10 it was deprecated. What should i do?

Instead of such puzzle i'd like to have something, which takes those technics correctly together, so beginner or any Unicode user could just say something like:

How could it break any older code?

Btw, i am still testing your last test block (first 3 are dependent of Perl which i don't trust completly itself). No major problems so far with files (named 'zzzⲊфӨ✺☻.txt' and 'zzzⲊфӨ✺☻.svg'), but i have limited network possibilities for now and no other OSes except Kubuntu. One tiny problem so far: Padre (!) file dialogs do not use my locale to sort files. So far i am pretty sure, that Linux main distros in core (system level) are Unicode ready, even if we can find some apps or other OSes which can't act together.