title: How to retrieve value of cons cell by key name?
body: <p>Say I have a list of cons cells like so:</p>
  
  <pre><code>(setq foo '(("a" . 1) ("b" . 2) ("c" . 3)))
  </code></pre>
  
  <p>And I'd like to retrieve the value of a particular cons cell by "key name". Is there a function that will let me do this?</p>
  
  <p>E.g.</p>
  
  <pre><code>(get-by-key "a" foo) ;; =&gt; 1
  </code></pre>
  
  <p>Or something similar. Thanks in advance!</p>