title: pipes are clogged - one shell pipe works, but two don't
body: <p>How to I get this to work? (Why does it not work?)</p>
  
  <pre><code>iostat -n9 -w 5 | gcut -c 14-20,34-40,54-60 | perl -p -e 's/(\d\.\d)\d/\1 /g'
  </code></pre>
  
  <p>By contrast,</p>
  
  <pre><code>iostat -n9      | gcut -c 14-20,34-40,54-60 | perl -p -e 's/(\d\.\d)\d/\1 /g' 
  </code></pre>
  
  <p>works fine.</p>
  
  <p>(Similarly, if each command is a letter,<br>
  <code>a | b | c</code> and <code>a | c | b</code> don't work,<br>
  but <code>a | b</code> and <code>a | c</code>  work fine.</p>
  
  <p>This is on macOS, if that matters.)</p>