documentation question

I recently installed sendmail 8.8 and in the documentation it says that in
procmail $1 is the sender and $2 is the recipient.  I tried setting a variable
to each value (ie SENDER=$1 and RECIPIENT=$2) in my /etc/procmailrc file but
didn't work.  Was the sendmail document wrong or am I misinterpreting what it
said?

Dorita