-In TO-STRING, \\& means insert what matched REGEXP,
-and \\=\\<n> means insert what matched <n>th \\(...\\) in REGEXP.
+In TO-STRING, `\\&' stands for whatever matched the whole of REGEXP,
+and `\\=\\N' (where N is a digit) stands for
+ whatever what matched the Nth `\\(...\\)' in REGEXP.
+
+If `query-replace-interactive' is non-nil, the last incremental search
+regexp is used as REGEXP--you don't have to specify it with the minibuffer.