Trying to insert new body+some newbie questions

Hello, all

I'm new in procmail and those are may be a simple questions but i want to 
understand how does it works:

1) i'm trying to save a copy of the message, replace the body with my own
   and forward this message to somebody. This is the part of my
   procmailrc file:

:0                              # Returned mail processing 
* ^From.*MAILER-DAEMON
* ^Subject: *Returned mail:
{
        :0 cw:                  # save copy into separate folder
        $RETURNFL

        :0 fbw                  # create new body 
        | cat /dev/null; \
          echo "Returned mail is received. See $RETURNFL folder."; \
          echo ""; \
          echo "MAIL ROBOT Romania."; \
          echo ""

        :0 fhw                  # change the header
        | formail -I"From: $MYADDR" -I"To: $ADMIN" \
                  -I"Subject: Romania Mail Robot ERROR - returned mail"

        :0                      # forward to administrator
        ! $ADMIN
}

The result is that $ADMIN gets only header of the message! This result is
also if I remove "cat /dev/null;" and I cannot understand why. May be
something wrong here or some other way must be used to do this?

2) When is important to use w flag? I read explanation about its meaning
  in man pages and proclist answers but it's still not clear for me.

3) What the meaning of the A and a flags? What does the difference between
   them? The man pages are really brief about this. 

Regards,
        Irena 

-----------------------------------------------------------------------
   Irena Rogatsky                       E-mail: 
irena(_at_)sysdep(_dot_)elex(_dot_)co(_dot_)il
   Database group                       Phone:  972-8-9774730
   Telrad Telecommunications