Changing layer parameters via CGI with underscore in name

[Nathan Vander Wilt]

Hello all! I have a layer defined similarly to this:

LAYER
 NAME 'dfirm_main'
 ...
END

I would like to change some parameters for this on the fly, however I'm wondering if how 
to deal with the underscored name in the map_ heirarchy, which depends on underscores as 
well. The following example does not work, although if I change the layer name to remove 
the underscore in both the .map and the url, then it does work as expected:

http://example/cgi-bin/mapserv?map=/var/www/maps/nvw-test/
test.map&map_dfirm_main_class_color=255+0+0&mode=map


How can I change parameters via CGI on a layer named with an underscore?

thanks,
-natevw