Does GNU Smalltalk support Unicode and MBCS?
Yes. Strings however are processed (e.g. read from a file) byte-per-byte. If you need per-character processing, you should load the Iconv package and convert strings to UnicodeString, using the #asUnicodeString method.
Regular expression matching cannot operate directly on UnicodeString objects. This means that regular expression matching will not work with most multi-byte character encodings (it will work with UTF-8).