Apache environment variables - logical AND

[Ian Smith]

I know this isn't FreeBSD specific - but I am, so crave your indulgence.

Running Apache 1.3.27, using a fairly extensive access.conf to beat off 
the most rapacious robots and such, using mostly BrowserMatch[NoCase] 
and SetEnvIf to moderate access to several virtual hosts.  No problem.

OR conditions are of course straighforward:

  SetEnvIf <condition1> somevar
  SetEnvIf <condition2> somevar
  SetEnvIf <exception1> !somevar

What I can't figure out is how to set a variable3 if and only if both 
variable1 AND variable2 are set.  Eg:

  SetEnvIf Referer "^$" no_referer
  SetEnvIf User-Agent "^$" no_browser

I want the equivalent for this (invalid and totally fanciful) match: 

  SetEnvIf (no_browser AND no_referer) go_away

Any clues?

cheers, Ian