title: Multiline sublime text language module definition
body: <p>I'm trying to create a new syntax definition for Sublime Text. I've worked out the regular expression to highlight a match within a each line but I'd like the match to include new lines as well as any character. Here's the regex from the tmLanguage file that works within a single line:</p>
  
  <pre><code>&lt;key&gt;match&lt;/key&gt;
  &lt;string&gt;\{\+\+(.*?)\+\+[ \t]*(\[(.*?)\])?[ \t]*\}&lt;/string&gt;
  </code></pre>
  
  <p>I've attempted to modify the the dot (.) matching to span multilines but it doesn't actually appear to capture the entire block. My understanding is that the modifier ?m: should work, but does not.</p>
  
  <pre><code>&lt;key&gt;match&lt;/key&gt;
  &lt;string&gt;(?m:(\{\+\+(.*?)\+\+[ \t]*(\[(.*?)\])?[ \t]*\}))&lt;/string&gt;
  </code></pre>
  
  <p>Is there a way to declare a language definition regex that will match across multiple lines?</p>