string matching

I want to replace a string using perl or sed or any other  which exactly matches, I have googled it but not find suitable for me.  Can some please help me in that case ?

Suresh R. Garge <garge.suresh1@gmail.com>



Got solution..! :) 

 s/\bgreen\b/mauve/g;  

Ref http://www.sarand.com/td/ref_perl_pattern.html

 Suresh R. Garge <garge.suresh1@gmail.com>