title: How to prepend a column to a matrix?
body: <p>Ok, imagine I have this Matrix: {{1,2},{2,3}}, and I'd rather have {{4,1,2},{5,2,3}}. That is, I prepended a column to the matrix. Is there an easy way to do it?</p>
  
  <p>My best proposal is this:</p>
  
  <pre><code>PrependColumn[vector_List, matrix_List] := 
   Outer[Prepend[#1, #2] &amp;, matrix, vector, 1]
  </code></pre>
  
  <p>But it obfuscates the code and constantly requires loading more and more code. Isn't this built in somehow?</p>