var extsprintf = require('extsprintf');
  var fs = require('fs');
  var verror = require('../lib/verror');
  
  function checkFile(filename, callback) {
  	fs.stat(filename, function (err) {
  		if (err)
  			/* Annotate the "stat" error with what we were doing. */
  			return (callback(new verror.VError(err,
  			    'failed to check "%s"', filename)));
  
  		/* ... */
  		return (callback());
  	});
  }
  
  function handleRequest(filename, callback) {
  	checkFile('/nonexistent', function (err) {
  		if (err)
  			/* Annotate the "checkFile" error. */
  			return (callback(new verror.VError(
  			    err, 'request failed')));
  
  		/* ... */
  		return (callback());
  	});
  }
  
  handleRequest('/nonexistent', function (err) {
  	if (err) {
  		console.log(err.message);
  		console.log(extsprintf.sprintf('%r', err));
  	}
  
      /* ... */
  });