assigning _ in the repl has side effects

Version: v4.2.3
Platform: Linux eric-ThinkPad-X220 3.19.0-51-generic Fix for path.resolve containing relative path to another drive in windows #57~14.04.1-Ubuntu SMP Fri Feb 19 14:36:55 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

In Nodejs REPL env, where var _ = require('lodash') failed to be assigned, but abc can.

> var _ = require('lodash');
undefined
> _
undefined
> var abc = require('lodash');
undefined
> abc
{ [Function: lodash]
  templateSettings: 
   { escape: /<%-([\s\S]+?)%>/g,
     evaluate: /<%([\s\S]+?)%>/g,
     interpolate: /<%=([\s\S]+?)%>/g,
     variable: '',
     imports: { _: [Circular] } },