checking return value of program called by procmail

Me again...

I have now rewritten my C filtering program, and it looks
as follows:

 ... rules ...

:0:
RESULT=| ( formail -XFrom: -XTo: -XCc: ; echo "Found: $FOUND" ) | \
        filterheaders

Now, filterheaders returns 0 or 1 (with return(0) or return(1) in C)
and I want that if the result is 1, the current message
is copied to the `my-default' folder.

Thanks in advance,

Denis