docs: function(prop) {
      var length = prefixes.length;
      var cssrule = window.CSSRule;
      var rule;
  
      if (typeof cssrule === 'undefined') {
        return undefined;
      }
  
      if (!prop) {
        return false;
      }
  
      // remove literal @ from beginning of provided property
      prop = prop.replace(/^@/, '');
  
      // CSSRules use underscores instead of dashes
      rule = prop.replace(/-/g, '_').toUpperCase() + '_RULE';
  
      if (rule in cssrule) {
        return '@' + prop;
      }
  
      for (var i = 0; i < length; i++) {
        // prefixes gives us something like -o-, and we want O_
        var prefix = prefixes[i];
        var thisRule = prefix.toUpperCase() + '_' + rule;
  
        if (thisRule in cssrule) {
          return '@-' + prefix.toLowerCase() + '-' + prop;
        }
      }
  
      return false;
    }