GHC now (as of early Jan 2006) interprets source files as UTF-8. In -fglasgow-exts mode the above special symbols are interpreted as in JHC. GHC knows about the characters classifications of all unicode characters via the Data.Char library, and can therefore understand identifiers written using alphanumeric characters from any language (but see below for note about caseless character sets).
for 6.10 We show how to build a quasiquoter for a simple mathematical expression language. Although the example is small, it demonstrates all aspects of building a quasiquoter. We do not mean to suggest that one gains much from a quasiquoter for such a small language relative to using abstract syntax directly except from a pedagogical point of view---this is just a tutorial!