performing diff on parts of a file

[Kamaraju Kusumanchi <kk288@cornell.edu>]

I am looking for a program/script(?) which performs diff on parts of a 
file. Say I have a file of 100 lines. How to do diff on lines between 
20-30, and 50-60 without writing them into separate files. Which 
software should I learn for this? sed/awk/perl?

thanks for any ideas
raju