it was tested, i just pasted the wrong variable name in a couple of places

:
on *:JOIN:#:{
if ($nick == $me) {
set $eval(%count. $+ $chan,2) 0
}
elseif ($nick != $me) {
inc $eval(%count. $+ $chan,2) 1
echo $chan i have seen $eval(%count. $+ $chan,2) users join this channel.
}
}
on *:PART:#:{
if ($nick == $me) {
unset $eval(%count. $+ $chan,2)
}
}