请指点 谢谢 使用.htaccess文件

目前在做二级域名转发，在httpd.conf里边修改虚拟主机的设置，写转发规则，已经实现当访问：http://aaa.maibuni.com 隐式转发到http://www.maibuni.com/htdocs/aaa/index.html

转发规则如下：
RewriteEngine on
RewriteCond %{HTTP_HOST} ^[a-z0-9\-]+\.maibuni\.com$
RewriteRule ^/(.*)$ /%{SERVER_NAME}/$1
RewriteRule ^/([a-z0-9\-]+)\.maibuni\.com/(.*)$ /opt/lampp/htdocs/popsnail/ $1/$2

但我的空间上不允许更改httpd.conf ，所以需要使用.htaccess文件
但写上上边同样的规则就显示错误，不知道为什么，请指教
显示错误如下：

Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.

Please contact the server administrator, webmaster@dummy-host.example.com and inform them of the time the error occurred, and anything you might have done that may have caused the error.

More information about this error may be available in the server error log.


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Apache/2.2.3 (Unix) DAV/2 mod_ssl/2.2.3 OpenSSL/0.9.8d PHP/5.2.0 mod_apreq2-20051231/2.5.7 mod_perl/2.0.2 Perl/v5.8.7 Server at pp.maibuni.com Port 80

请指点 谢谢