Well, that bit in the pod about matching GB characters was based on personal experience. Access to Perl 5.8's character-set transliteration and unicode-based character semantics for matches (not to mention the very handy "\p" unicode-based character classes) was the main reason I had to write this tool in the first place. The other bells and whistles (handling compressed data, controlling the input record separator) were after-thoughts -- once I started using this thing on real (multi-language, multi-coded) text data, those other things were just handy and easy to add. But the Encode module was crucial.
Maybe some people have tricks to search for a specific GB (or Big5, or Shif-JIS) character using plain-old "grep", but I couldn't figure a way to make it trustworhty for such things, and doing it with Perl just made sense.