60:  How do I use regexps (regular expressions) in Emacs?
  
  See `Regexps' in the online manual.
  
  WARNING: The "or" operator is `\|', not `|', and the grouping operators
  are `\(' and `\)'.  Also, the string syntax for a backslash is "\\".
  Thus, the string syntax for a regular expression like xxx\(foo\|bar\) is
  "xxx\\(foo\\|bar\\)".  Notice the duplicated backslashes!
  
  WARNING: Unlike in Unix grep, sed, etc., a complement character set
  ([^...])  can match a newline character (LFD aka C-j aka \n), unless
  newline is mentioned as one of the characters not to match.
  
  WARNING: The character syntax regexps (eg. `\sw') are not meaningful
  inside character set regexps (eg. `[aeiou]').  (This is actually typical
  for regexp syntax.)