program | tee >(wc -l)

program | awk '{ print } END { print NR }'

program | perl -pe 'END {print "$.n"}'

program | sed -n 'p;$='

program | tee /dev/stderr | wc -l

tail -f /var/log/squid/access.log | ( c=0; pl() { echo $c; c=0; }; trap pl SIGHUP; while read a; do (( c=c+1 )); done ) & ( trap 'kill $! ; exit' SIGINT; trap '' SIGHUP; while true; do kill -HUP $! ; sleep 1; done)