This chapter is about MH. But if you use a front-end (like xmh), you might want to read this chapter anyway because there are some useful programs here -- you can always exit for a while, open another window, run these programs, and then restart xmh.
The chapter takes you through the process of making a new MH command version step by step. The initial setup and the first new command or two can be a little tough for someone who's not particularly familiar with UNIX. After that, though, you'll be thinking of and creating new command versions of your own.
For instance, if you want to let someone know that you got their message, here's a version of repl that automatically sends a "thank you." Receptionists can send telephone messages through email with a version that prompts them for the parts of the message. There are versions of scan that give you extra information without lots of extra typing.
As much as anything, this chapter should give you ideas for changes that will make MH work your way.