12.7 Exercises with re-search-forward

• Write a function to search for a regular expression that matches two or more blank lines in sequence.
• Write a function to search for duplicated words, such as ‘the the’. See Syntax of Regular Expressions in The GNU Emacs Manual, for information on how to write a regexp (a regular expression) to match a string that is composed of two identical halves. You can devise several regexps; some are better than others. The function I use is described in an appendix, along with several regexps. See the-the Duplicated Words Function.