code: function _regExpOrGTFO(expr){
    var exp;
  
    if(typeof expr === 'string'){
      exp = new RegExp('^'+expr+'$');
    } else if (expr instanceof RegExp){
      exp = expr;
    } else {
      throw new Error('Needle must be either a string or a RegExp');
    }
  
    return exp;
  }
docs: Cohearses `expr` into a RegExp or throws an error if it can't
  @private
  @param  {Mixed}  expr RegExp or string.
  @return {Object}      Strict Regular Expression version of string