Mod_rewite HTTP_USER_AGENT with RewriteMap

Hi group,

OK so I'm trying to append a query string [QSA] based on a partial user
agent match. The match is to distinguish screen based browsers from
handheld browsers. Now I'd like to do this through a RewriteMap.

At the moment I have this:

RewriteMap agent_compact txt:/etc/httpd/conf/sites/useragentCompact.map
RewriteCond %{%{HTTP_USER_AGENT}:agent_compact|MISS} !=MISS
RewriteRule ^/(.+)$ /$1?mode=${agent_compact:$1|compact} [QSA]

However I'm unclear as to the form the *.map file should take, I'
assuming something like?:

Firefox default
up.Browser compact

Is this right? I also think my RewriteCond and RewriteRule is flawed.

TIA