Apache Redirect within public_html (~username)

[Michael Torrie]

I have a url, say, http://blah/~torriem/blah that I want to redirect
with a 301 into a particular wiki page, say

http://blah/~torriem/wiki/blah

I know how to do the Redirects from inside the apache conf file.  How
can I do this in an .htaccess file in my public_html directory?

Also, my server is accessible via a specific hostname, but sometimes I
access it by IP address over a VPN.  The Redirect keyword requires a
complete url to redirect to.  Is there any way to redirect to the new
path but make sure the hostname part is the same as the original request?

Do I need to do a Rewrite instead?