Bad error message for block pass through with return statement

```
alex@alex-gaynor-laptop:~/projects/rupypy$ ruby-1.9.3-p125 -e "return &5"
-e:1: block argument should not be given
alex@alex-gaynor-laptop:~/projects/rupypy$ jruby-1.6.7 -e "return &5"
SyntaxError: -e:1: Dynamic constant assignment.
```
