Remember that the case structure is based on a string in this case, even if you are thinking in terms of chars.
Let's say that the upper limit was inclusive, then to match strings which start with A,B, and C [A..C] you would have to specify the "largest" string which begins with C, is it CZZZZ or CZZZZZZZZ or C\xFF\xFF\xFF.... etc. The way it is now you can do [A..D)
The same issue complicates adding floats to the case selector options.
One solution is to add the ability to specify the inclusiveness of the boundaries. The normal method is [,] for inclusion and (,) for exclusion. Then you could write [A..D) for strings and [A..C] for chars. And you could add floats to the Case structure as well.
Another is to allow U8's to be viewed as their ascii equivalent so you could use those more readily. Same as selecting the radix.
Another option is to have an option to match only the first char of the string and make the limit inclusive in that specific case.
