Search engine keywords in Firefox

Hai,
I've been playing around with some keywords for search engines in firefox as I have just realised that I can use them as shortcuts in the address bar. (prior to this I had been using URL Alias, an extension offering similar capabilities).
What I'm hoping to do is set up some searches for a few sites, but if no keyword is used it will search google. For example, I have these keywords

w <search phrase> (searches wikipedia)
f <search phrase> (searches flicker)
v <search phrase> (searches vimeo)

And I want to make it so if I type "w Mac" I will be taken to en.wikipedia.org/wiki/Mac but if I type "Mac" I'll be taken to google.com/search?q=mac

I have found I cannot use a wildcard * as a keyword when adding a keyword in my google search engine in the manage search engine dialog, and if I set it up with URL Alias it will work but it overides everything (As in typing w Mac will search google for "w Mac")

Can anybody suggest what I can do to work around this?
Thanks in advance! -Tim

With a bit of extra googling I was able to find a greasemonkey script that redirects an OpenDNS search page to a google search... seems to do what I want!
For people who don't use OpenDNS (Which you should!) you can change the keyword.URL key in about:config to a google search page.

Thanks clevin, that's I've just been doing... I was hoping I might be able to have google search as default if there is no keyword. and not a URL...

I think this greasemonkey script is the only sollution, I couldn't find anything in my OpenDNS settings.

Any other solutions are appreciated!