Clarifying the clarification: Actually, what OP said was "The version is not always of the same format." The request is for sufficient info to have some notion of the range of variant formulae possible.

If all the possibilities in that range are (readily) amenable to recognition with a regex, then the question of which kind of "'Multibyte' characters" might help in writing a regex.

If the range would make regex|regexen unacceptable (read, for example, as: 'so complex as to make execution unacceptably slow'), then another approach is required.

Perhaps the above is simply a more precise reforumulation of your intent in para 1. If so, well done!