code: function checkEnv(tmp) {
        if(typeof tmp === 'string') {
          var up = tmp.toUpperCase();
          if(up.indexOf("$ENV:") !== -1) {
            var envVariable = tmp.substr(5).trim();
            if(typeof process.env[envVariable] === 'undefined') {
              console.error('Environment variable: %s is missing, in config file: %s', envVariable, self.path);
              return;
            }
            return process.env[envVariable];
          }
          if(up.indexOf('$ARGV:') !== -1) {
            var argName = tmp.substr(6).trim(),
              argVal = crux.argv(argName);
            if(!argVal) {
              console.error('Argv variable: %s is missing, in config file: %s', argName, self.path);
              return;
            }
            return argVal;
          }
          return;
        }
        if(typeof tmp === 'object' && tmp !== null) {
          if(tmp instanceof Array) {
            for(var i= 0, len = tmp.length; i < len; i++) {
              var replacedVar = checkEnv(tmp[i]);
              if(typeof replacedVar !== 'undefined') {
                tmp[i] = replacedVar;
              }
            }
            return;
          }
          for(var key in tmp) {
            var replacedVar = checkEnv(tmp[key]);
            if(typeof replacedVar !== 'undefined') {
              tmp[key] = replacedVar;
            }
          }
        }
      }
docs: If we have a configuration parser, we first look for $ENV: variables.