title: Regular expression for no whitespaces on the first position
body: <p>Example accepted:</p>
  
  <blockquote>
  <pre><code>This is a try!
  And this is the second line!
  </code></pre>
  </blockquote>
  
  <p>Example not accepted:</p>
  
  <blockquote>
  <pre><code>      this is a try with initial spaces
  and this the second line
  </code></pre>
  </blockquote>
  
  <p>So, I need:</p>
  
  <ul>
  <li>no string made only by whitespaces " "</li>
  <li>no string where first char is whitespace</li>
  <li>new lines are ok; only the first character cannot be a new line</li>
  </ul>
  
  <p>I was using</p>
  
  <pre><code>^(?=\s*\S).*$
  </code></pre>
  
  <p>but that pattern can't allow new lines.</p>