I'm implementing a Tetris game in Lisp (Common Lisp), a language I'm not familiarized with, and I've come up with an error which I don't really understand why it's happening.

```
(defun tabuleiro-remove-linha! (tabuleiro linha)
    (let ((coluna 0))
        (if (equal linha 17)
            ((loop while (<= coluna 9) do(setf (aref tabuleiro linha coluna) nil)))
            ((loop while (<= coluna 9) do((setf (aref tabuleiro linha coluna) (aref tabuleiro (+ linha 1) coluna)))
             (tabuleiro-remove-linha! tabuleiro (+ linha 1)))))))

```

It's showing:

```
TABULEIRO-REMOVE-LINHA! in lines 51..56 : Not the name of a function:
     (LOOP WHILE (<= COLUNA 9) DO (SETF (AREF TABULEIRO LINHA COLUNA) NIL))
If you continue (by typing 'continue'): Ignore the error and proceed

```

Any clues? I have searched and both loop and while exist in CLISP. My CLISP is 2.49. Thanks in advance.