apache manual 中关于url rewrite规范化URL的写法不理解

QUOTE:

Canonical URLs

Description:

    On some webservers there are more than one URL for a resource. Usually there are canonical URLs (which should be actually used and distributed) and those which are just shortcuts, internal ones, etc. Independent of which URL the user supplied with the request he should finally see the canonical one only.
Solution:

    We do an external HTTP redirect for all non-canonical URLs to fix them in the location view of the Browser and for all subsequent requests. In the example ruleset below we replace /~user by the canonical /u/user and fix a missing trailing slash for /u/user.

    RewriteRule   ^/~([^/]+)/?(.*)    /u/$1/$2  [R]
    RewriteRule   ^/u/([^/]+)$  /$1/$2/   [R]

CODE:

RewriteEngine On
RewriteRule   ^/~([^/]+)/?(.*)    /u/$1/$2  [R]
RewriteRule   ^/u/([^/]+$  /$1/$2/   [R]

QUOTE:

192.168.254.1 - - [02/Feb/2009:22:38:31 +0800] "GET /~testuser/ HTTP/1.1" 302 219
192.168.254.1 - - [02/Feb/2009:22:38:31 +0800] "GET /u/testuser/ HTTP/1.1" 404 207
192.168.254.1 - - [02/Feb/2009:22:38:37 +0800] "GET /u/testuser/ HTTP/1.1" 404 207

CODE:

RewriteEngine On
RewriteRule ^/index.html$  /index.htm