61:  How do I perform a replace operation across more than one file?
  
  The "tags" feature of Emacs includes the command tags-query-replace which
  performs a query-replace across all the files mentioned in the TAGS file.
  See `Tags:Tags Search' in the online manual.
  
  In addition, Martin Boyer has written a package named global-replace which
  will perform a query-replace across all the files mentioned in the
  *compilation* buffer (usually done after a `grep'), which is available via
  anonymous FTP (ireq-robot.hydro.qc.ca:
  pub/emacs/lisp/{compile,global-replace,query}.el.Z).