title: Why is modulus different in different programming languages?
body: <p>Perl</p>
  
  <pre><code>print 2 % -18;
  </code></pre>
  
  <p>--></p>
  
  <pre><code>-16
  </code></pre>
  
  <p>Tcl</p>
  
  <pre><code>puts [expr {2 % -18}]
  </code></pre>
  
  <p>--></p>
  
  <pre><code>-16
  </code></pre>
  
  <p>but VBScript</p>
  
  <pre><code>wscript.echo 2 mod -18
  </code></pre>
  
  <p>--></p>
  
  <pre><code>2
  </code></pre>
  
  <p>Why the difference?</p>