What if you want to exchange @samp{x} and @samp{y}: replace every @samp{x} with a @samp{y} and vice versa? You can do it this way:
@example
-M-x query-replace @key{RET} x @key{RET} @@TEMP@@ @key{RET}
-M-x query-replace @key{RET} y @key{RET} x @key{RET}
-M-x query-replace @key{RET} @@TEMP@@ @key{RET} y @key{RET}
+M-x replace-string @key{RET} x @key{RET} @@TEMP@@ @key{RET}
+M-< M-x replace-string @key{RET} y @key{RET} x @key{RET}
+M-< M-x replace-string @key{RET} @@TEMP@@ @key{RET} y @key{RET}
@end example
@noindent
@noindent
performs the inverse transformation.
+ You can also use arbitrary Lisp expressions evaluated at replacement
+time by placing @samp{\,} before them in the replacement string. Inside
+of those expressions, the symbols @samp{\&} and @samp{\@var{d}} refer to
+match and submatch strings like described above (a submatch not matching
+anything will be @samp{nil}), and @samp{\&#} and @samp{\@var{d}#} to
+those strings converted to numbers. @samp{\#} is short for
+@samp{replace-count}, the number of already completed replacements.
+This particular shorthand can also be used outside of @samp{\,}.
+
+ Repeating our example to exchange @samp{x} and @samp{y}, we can thus
+do it also this way:
+
+@example
+M-x replace-regexp @key{RET} \(x\)\|y @key{RET}
+\,(if \1 "y" "x") @key{RET}
+@end example
+
+ Another feature you can use in the replacement string of Regexp
+commands is @samp{\?}. In that case you will be allowed to edit the
+replacement string at the given position before the replacement gets
+performed. Lisp style replacements have already been done before
+@samp{\?} is executed. For example,
+
+@example
+M-x replace-regexp @key{RET} \footnote@{ @key{RET}
+\&\\label@{fn:\#\?@} @key{RET}
+@end example
+
+@noindent
+will add labels starting with @samp{\label@{fn:0@}} to occurences of
+@samp{\footnote@{}, but letting you edit each replacement before
+performing it. If you want labels starting at 1, use @samp{\,(1+ \#)}
+instead of @samp{\#}.
+
+As another example, to add consecutively numbered strings like
+@samp{ABC00042} to column 73 to~80 (unless they are already occupied),
+you can use
+
+@example
+M-x replace-regexp @key{RET} ^.\@{0,72\@}$ @key{RET}
+\,(format "%-72sABC%05d" \& \#) @key{RET}
+@end example
+
@node Replacement and Case, Query Replace, Regexp Replace, Replace
@subsection Replace Commands and Case
@item ^
to go back to the position of the previous occurrence (or what used to
-be an occurrence), in case you changed it by mistake. This works by
-popping the mark ring. Only one @kbd{^} in a row is meaningful, because
-only one previous replacement position is kept during @code{query-replace}.
+be an occurrence), in case you changed it by mistake or want to
+reexamine it.
@item C-r
to enter a recursive editing level, in case the occurrence needs to be