This particular project needs a module which will take a string input from the keyboard, and has to carry out character-by-character replacing using the ROT13 process(A is replaced with N, etc) and has to ignore capitalization differences, ignoring other characters from the alphabetic set, with the option of continuing the same process with another input or exit the program.
I have been designing such modules from the past 3 years and if given a chance to do this, i could give you a perfect module, like i have done in the past.