strange behaviour

I set procmailrc in this way:
....

STORIA=pippo(_at_)ptnet(_dot_)it
:0 cw
* $ !^X-Loop: $STORIA
{
     :0 fw
     | ( formail  -A"X-Loop: $STORIA"  -I"To: $STORIA"  ) \
       | $SENDMAIL -oi -t
}

I want send a copy of the mail at $STORIA.
I noted that if pippo(_at_)ptnet(_dot_)it doesn't exist I receive the mail 
twice.
Why?

this is the log:

procmail: Match on ! "^X-Loop: pippo(_at_)ptnet(_dot_)it"
procmail: Forking "procmail"
procmail: [4498] Thu Apr 19 11:25:17 2001
procmail: Executing " ( formail  -A"X-Loop: $STORIA"  -I"To: $STORIA"  )
\
       | $SENDMAIL -oi -t"
procmail: [4498] Thu Apr 19 11:25:17 2001
procmail: Program failure (67) of " ( formail  -A"X-Loop: $STORIA" 
-I"To: $STORIA"  ) \
       | $SENDMAIL -oi -t"
procmail: Rescue of unfiltered data succeeded
procmail: [4498] Thu Apr 19 11:25:17 2001


Michele
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