-If the second parameter is `undef`, the URL will be valid from any page on the
-wiki, or from the CGI; if possible it'll be a path starting with `/`, but an
-absolute URL will be used if the wiki and the CGI are on different servers.
+If the second parameter is not specified (or `undef`), the URL will be
+valid from any page on the wiki, or from the CGI; if possible it'll
+be a path starting with `/`, but an absolute URL will be used if
+the wiki and the CGI are on different domains.