You can use $count() in place of || and isin like so:

if (Last seen time: isin $1-) || (Last quit message: isin $1-) { msg %seen $1- }

compared to:

if ($count($1-,last seen time:,last quit message:)) { msg %seen $1- }

These two conditions are pretty much the same thing, but one is shorter than the other as shown.