In the Mail gem I am doing Regexp's on various strings that arrive,
which can be basically anything (user defined). So I am dup'ing the
string, and forcing the encoding to binary before I do the regexp...
but I am getting this warning:

~/lib/mail/utilities.rb:56: warning: regexp match /.../n against to UTF-8 string

The code that produces that is:

    aspecial     = %Q|()<>[]:;.\\,"|
    control      = %Q|\x00-\x1f\x7f-\xff|
    PHRASE_UNSAFE = /[#{Regexp.quote aspecial}#{control}]/n

    def quote_phrase( str )
      if RUBY_VERSION >= '1.9'
        string = str.dup
        string.force_encoding('ASCII-8BIT')
        (PHRASE_UNSAFE === string) ? dquote(str) : str
      else
        (PHRASE_UNSAFE === str) ? dquote(str) : str
      end
    end

Any clues?

The specs that generate these errors all pass, so the Regexp is doing
what I intend it to do from what I can see.

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