redirectMatch in mod rewrite - apache

Question

We recently moved our web site to another server, say http://newdomain.com, while our old site is at say http://olddomain.com
I would like to keep the users directory on the old site accessible as it was before, that is http://oldomain.com/~user, but anything accessible under the root folder point to the new domain. The users directory on the old server are in the /home/user file system. So, I wrote following rules:
RedirectMatch permanent ^/~(.*) /home/~$1
RedirectMatch permanent ^/(.*) http://newdomain.com/$1
while the second rule works flawlessly, the first one still wants to map to the new site as following: http://newdomain.com/~user.
How can I fix the two rules so that anything in /var/www/html on the old site redirects to the new site, but anything under /home does not redirect?
--
Here is the new code based on Ben's solution, which maps the urls for the access to users' home pages correctly, but the browser complains and does not show their sites. The root folder urls redirection works fine.
RewriteEngine on
# RewriteBase / -- I had to comment this as the apache did not like it
Rewriterule ^/~(.*) /~$1 [R=301,L]
RewriteCond %{REQUEST_URI} !^/home/~
RewriteRule ^/(.*) http://newdomain.com/$1 [R=301,L]

Answer 1

You should use RewriteCond to test if the URI prefix with /home/~, and use RewriteRule to rewrite the URL and make a permanent redirect.
RewriteEngine On
RewriteBase /
RewriteRule ^~(.*) /home/~$1 [R=301,L]
RewriteCond %{REQUEST_URI} !^/home/~
RewriteRule ^(.*) http://newdomain.com/$1 [R=301,L]
Line 3: if URI prefix with ~{any_characters}, rewrite the URI to /home/~{any_characters}, redirect permanently
Line 5: Test if the URI not prefix with /home/~{any_characters}
Line 6: Then process the rewrite rule, rewrite the URI from {any_characters} to http://newdomain.com/{any_characters}, redirect permanently