(define copy-lumbda
        (lambda (z)
                (dmatch z
                        [,sym (guard (or (symbol? sym) (number? sym))) sym]
                        [(lambda (,expr),body) (append (cons 'lumbda (list (list (copy-lumbda expr)))) (cons (copy-lumbda body) '()))]
                        [(,M1 ,M2) (append (list (copy-lumbda M1)) (list (copy-lumbda M2)))])))