> Ok fair enough. I've noticed that having the \ doesn't hurt for a dash.
> Now what about matching a question mark and an equals sign?

If you read perlre closely you will find it says that it never hurts to put
a backslash before a special character that you want to match as a
character. So this is a case of "does nothing, but doesn't hurt".

> I've read perlre and perlretut and understand regular expressions, but
> there is no clear cut way of matching these characters, either outlined
> by this document or any Spamassassin document I've come across so far.

For the most part you can match any character by the appearance of the
character. Any character with special meaning needs to be escaped in some
way. The easiest way is usually with a backslash, but in some cases you can
also do it by making it a member of a character class.

So for you questionmark case, you could do \? or [?], as most of the special
characters lose their meaning in a character class. The exceptions are
obviously right bracket, backslash, and dash becomes special if it isn't the
first character.

> /\=\?koi8\-r\?/

This should work. You don't need to escape the dash, and I'm pretty sure
you don't need to escape the equal sign; just the questionmark.

Also, you may want to handle this in both uppercase and lowercase, so you
could do


And you probably don't need the = sign to get reasonably reliable matching.