[XeTeX] String manipulation (substr and similar) in XeLaTeX

[Jan Zahornadsky]

Hi!

I've just came over this problem -- is there a package or method how to
manipulate strings (as packages like coolstr, substr and similar do)?
They seem to work with XeLaTeX as long as the parameter contains no
special symbols (the 128 same-mapped characters, I suppose).

How to perform similar manipulations in the unicode? Are there some
built-in functions in XeLaTeX? Is it at least possible (by updating
existing packages)?

Thanks a lot in advance for any answer, any idea!
Jan