title: How can I apply Unix's / Sed's / Perl's transliterate (tr) to only a specific column?
body: <p>I have program output that looks like this (tab delim):</p>
  
  <pre><code>    $ ./mycode somefile 
      0000000000000000000000000000000000      238671
      0000000000000000000000000000000001      0
      0000000000000000000000000000000002      0
      0000000000000000000000000000000003      0
      0000000000000000000000000000000010      0
      0000000000000000000000000000000011      1548.81
      0000000000000000000000000000000012      0
      0000000000000000000000000000000013      937.306
  </code></pre>
  
  <p>What I want to do is on FIRST column only: replace 0 with A, 1 with C, 2 with G, and 3 with T.
  Is there a way I can transliterate that output piped directly from "mycode".
  Yielding this:</p>
  
  <pre><code>AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA        238671
  ...
  AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAACT        937.306
  </code></pre>