(Apache) RedirectMatch regex to match all directories except those in the list

I need to 301 redirect all requests coming in for requests to http://server.com to be redirected to http://newserver.com unless the request is for an arbitrary list of directories we are maintaining on the legacy server (eg server.com/foo or server.com/bar)

I'm having a hard time working out how best to set this up and the regexs.

EG, I need:

• http://server.com/page1 to redirect to http://newserver.com/page1
• http://server.com/dir1/page2 to redirect to http://newserver.com/dir1/page2
• http://server.com/foo to load as normal
• http://server.com/bar/baz.html to load as normal

… because 'foo' and 'bar' are in my list of legacy dirs.

I'm wondering if the way to do this is to some how catch the matches in my list and then redirect anything else as a wildcard over to the new server — but I can't make it work.

Can anyone help me with some regex and rewrites for those please?

Thanks