eyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Key<span class="special">,</span> <span class="keyword">typename</span> Env<span class="special">&gt;</span> 
  <span class="keyword">typename</span> <a class="link" href="result_of/env_var.html" title="Struct template env_var">proto::result_of::env_var</a><span class="special">&lt;</span><span class="identifier">Env</span> <span class="keyword">const</span> <span class="special">&amp;</span><span class="special">,