> (define-library (srfi nnn)
>    (export λ)
>    (import (scheme base))
>    (begin (define-syntax λ (syntax-rules () ((λ . rest) (lambda .
> rest))))))

Better yet:

(library (srfi :nnn)
   (export λ)
   (import (rename (only (rnrs base) lambda) (lambda λ))))

(define-library (srfi nnn)
   (export |\x3bb;|)
   (import (rename (only (scheme base) lambda) (lambda |\x3bb;|))))