Years ago, Albert Heinle was writing his thesis. A common error that many or most writers must deal with is using the same word repeatedly in close proximity. I certainly do and so did Heinle. He was using Emacs and LaTeX to write his thesis and he looked around for some software to automatically check for a repeated word within a given radius. He couldn’t find one but he was using Emacs so he wrote his own.
Heinle recently came across his word repetition code and decided to make it available to anyone who needs it. He says he used the project to learn Elisp so the code should be considered beta quality. He’s promised to work on it and it is, in any event, a single file so it should be easy to adapt it for your own uses.
When I’m writing an Irreal post, I generally go over it several times editing as I go. Just before I publish it I make one more pass. The most common problem I find is reusing the same word within two or three sentences.
If you write prose and find yourself repeating words too often, try out Heinle’s repetition detector. Perhaps it will help.