cannot pipe command in procmail

I don't seem to be able to execute a command and pipe the output
to another command!

Please help.

My procmail recipe:
-------------------
:0
* ^Subject:.*retrieve
| (formail -r; /bin/cat $HOME/bb/README) > $HOME/ttt


The log file shows:
-------------------
procmail: Assigning "INCLUDERC=/home/is/pta/.procmail/rc.main"
procmail: Match on "^Subject:.*retrieve"
procmail: Executing " (formail -r; /bin/cat $HOME/bb/README) > $HOME/ttt"
procmail: Assigning "LASTFOLDER= (formail -r; /bin/cat $HOME/bb/README) > 
$HOME/ttt"
> From phong_ta  Wed May 28 11:51:25 1997
 Subject: retrieve
  Folder:  (formail -r; /bin/cat $HOME/bb/README) > $HOME/ttt               605
procmail: Notified comsat: "pta@: (formail -r; /bin/cat $HOME/bb/README) > 
$HOME/ttt"
procmail: Assigning "EXITCODE=0"
procmail: Executing "/bin/rm,-f,/home/is/pta/tmp/pmail.19123"
--------------------

But the file $HOME/ttt was not created!

Thanks,

-- 
Phong Ta
Motorola Advanced Messaging Group