I remember reading some explanation about the command line option
"--script", but I do not fully understand it. Now I have got a script which
shows significantly different results depending on whether it is run with
or without "--script".  I would like to know how this happens.

Here is my test case.

$ java kawa.repl -e '(scheme-implementation-version)'
3.1.1 (git describe: 3.1.1-0-gc47de33ad)$
$ cat 0.scm
(include "01.scm")
(include "02.scm")
(display (format #f "~a ~a ~a ~%" a1 a2 aa))
$ cat 01.scm
;; This is 01.scm
(define aa '())

(define-syntax define-a
  (syntax-rules ()
    ((_ a p)
       (begin
          (define a p)
          (set! aa (cons a aa))))))
$ cat 02.scm
;; This is 02.scm
(define-a a1 1)
(define-a a2 2)
$ java kawa.repl 0.scm
1 2 (2 1)
$ java kawa.repl --script 0.scm
/home/kaz/02.scm:3:1: duplicate declaration of 'aa'
/home/kaz/02.scm:3:1: (this is the previous declaration of 'aa')
$