I won’t use it, its indentation is very off.

take here: b is the body of the lambda function, but its indented as if its the body of the `letrec`

    (syntax (letrec ((f (lambda (a ...)
              b
              ...)))

or here

  
(define-syntax aif  
  (lambda (x)  
(syntax-case x ()  
((\_ test then else)  
(with-syntax ((it (datum->syntax x 'it)))  
\#'(let ((it test))  
(if it then else)))))))