title: Regular expression: between brackets, starts with a specific string but do not ignore spaces
body: <p>I am trying to extract from a string all unique occurrences of a specific pattern. My string is<br>
      <code>text = 'My name is {{user_name}} {{user_second name}}. I am {{anything_else}}'</code><br>
  I want to extract the text inside the double brackets that start with "user_". For the given string I would like to have the following array<br>
  <code>["user_name", "user_second name"]</code>.<br>
  I am trying to achieve this using the following regular expression but in case there is a space inside the square brackets it ignores it somehow.<br>
  <code>text.scan(/\{{(customer_\w*)\}}/).uniq.flatten</code> returns <code>["user_name"]</code></p>
  
  <p>Any help would be really appreciated.</p>