title: Filter ONLY several words (not the complete line) through an external command
body: <p>I'd like to use an external <a href="https://github.com/ap/titlecase" rel="nofollow">Perl</a> or <a href="https://launchpad.net/titlecase.py" rel="nofollow">Python</a> script to change a selection of text in Vim into <a href="http://en.wikipedia.org/wiki/Letter_case#Headings_and_publication_titles" rel="nofollow">title case</a>. As a user of these scripts, you can select the small words which are not capitalized.</p>
  
  <p>However, I want to apply the filter only on a part of a line, not the complete line. Does anyone know how to do this?</p>
  
  <p>Example line in LaTeX source code:</p>
  
  <pre><code>\item the title case in latex and ...
  </code></pre>
  
  <p>Should become</p>
  
  <pre><code>\item The Title Case in Latex and ...
  </code></pre>
  
  <p>The following command does not work:</p>
  
  <pre><code>:{visual}!{filter}
  </code></pre>