Make exception to whole-site RedirectMatch rule

Any reason you don't want to use mod_rewrite?

You could mimic the functionality with this:

RewriteCond  %{REQUEST_URI}  !^/(somepath|someotherpath)
RewriteRule  (.*)                       $1                        [R=permanent]
RewriteRule  http://%{SERVER_NAME}(.*)$1  [L]

I hadn't realized Apache uses PCRE. Since it does, you can do this bit of voodoo to do what you want with mod_alias:

RedirectMatch permanent ^/?((?!(thisisfoo|thisisbar)).*)$1

where /thisisfoo and /thisisbar are exceptions to the redirect.