title: Erlang: no match of right hand side value
body: <p>A common error message in Erlang programs is the following:</p>
  
  <pre><code>** exception error: no match of right hand side value 'foo'
       in function module:function/2 (file.erl, line 42)
  </code></pre>
  
  <p>How can I debug this?</p>