title: Matching strings with grep and \A regexp
body: <p>Given the string in some file:</p>
  
  <pre><code>hel           string1
  hell          string2
  hello         string3
  </code></pre>
  
  <p>I'd like to capture just <code>hel</code> using <code>cat file | grep 'regexp here'</code></p>
  
  <p>I tried doing a bunch of regexp but none seem to work. What makes the most sense is: <code>grep -E '\Ahel'</code> but that doesn't seem to work. It works on <code>http://rubular.com/</code> however. Any ideas why that isn't working with <code>grep</code>?</p>
  
  <p>Also, when pasting the above string with a tab space before each line, the <code>\A</code> does not seem to work on <code>rubular</code>. I thought <code>\A</code> matches beginning of string, and that doesn't matter whatever characters was before that. Why did <code>\A</code> stop matching when there was a space before the string?</p>