title: in Elixir: string formatting
body: <p>I have a transform rule: </p>
  
  <pre><code>"0549$2"
  </code></pre>
  
  <p>How do I apply this rule to strings in an Elixir?
  In ruby i use:</p>
  
  <pre><code>format("0549%2$s", *["88", "77"])
  =&gt; "054977"
  </code></pre>
  
  <p>In Elixir I write:</p>
  
  <pre><code>:io.format("0549%2$s", ["88", "77"])
  ** (ArgumentError) argument error
      (stdlib) :io.format(#PID&lt;0.54.0&gt;, "0549%2$s", ["88", "77"])
  </code></pre>
  
  <p>Because :io.format from erlang does not understand this format</p>