bytes::substr() ?

I'm working with a byte oriented protocol, and need to extract byte n1 through
byte n2 from a string. Problem is, the string can be UTF8, and substr() is 
character oriented. What (if anything) is the best way to do this in Perl?

Any/all ideas welcome. I would prefer a pure Perl (non XS) solution, but if
that's the way to go then that's the way to go. 

//Ed

-- 
Ed Summers
aim: inkdroid
web: http://www.inkdroid.org

"The deeper I go the darker it gets." - Peter Gabriel