title: Sed regex in bash issues
body: <p>Can someone tell me why this sed below doesn't work    </p>
  
  <pre><code>...| sed -E $'s/^\d/blah/g'
  </code></pre>
  
  <p>vs this one works?</p>
  
  <pre><code>| sed -E $'s/^/blah/g'
  </code></pre>
  
  <p>sample: </p>
  
  <pre><code>echo "10/30/18 04:45:13 PM EDT" | sed -E $'s/^/blah/'
  </code></pre>
  
  <p>Updated desire:</p>
  
  <pre><code>echo "10/30/18 04:45:13 PM EDT" | 
  sed 's/^[[:digit:]][[:digit:]]\/[[:digit:]][[:digit:]]\/[[:digit:]][[:digit:]]/\blah\n/'
  
  blah
  10/30/18 04:45:13 PM EDT
  </code></pre>