Bug: Perl-based reader doesn't handle a comment in the middle of an empty set of parens correctly

This code, when stored in a file and run from the command line:

```
(
; comment
)
```

Fails with this error message:

```
Error: ('unboundb )
```

But the same code, when fed through the Bel reader on the REPL:

```
> (set s (append "(" (list \lf) "; comment" (list \lf) ")"))
"(
; comment
)"
> (read (list s))
nil
```

Works and gives the correct result `nil`.
