Node REPL that doesn't clobber _

console.js

var repl = require('repl')
var vm = require('vm');

var _;

var server = repl.start({
  eval: function (cmd, context, filename, callback) {
    try {
      var match = cmd.match(/^\((.*)\n\)$/);
      var code = match ? match[1] : cmd;
      context._ = _;
      var result = vm.runInThisContext(code, filename);
    } catch (error) {
      console.log(error.stack);
    } finally {
      _ = context._;
      callback(null, result);
    }
  }
}).on('exit', function () {
  process.exit(0);
});

Note one deficiency relative to just running node: You can't enter code that spans more than one line. You'll get a syntax error. Haven't figured that one out yet.