CLI: REPL: comments would cause SyntaxError like "return __ = ;// comments" which breaks code exec.

coffee>.editor
```coffeescript
# comments
1+2
```
return __ = (, 1 + 2);// comments
_____________^
SyntaxError: Unexpected token ,

OR
coffee>.editor
```coffeescript
###
comments
###
1+2
```
return __ = (, 1 + 2);/*
____________ ^
SyntaxError: Unexpected token ,