Sorry I wasn't clear.
on *:text:.seen &:#:{
if (%seen. [ $+ [ $nick ] ]) { return }
msg $chan $2 was last seen $read(text.txt)
set -u5 %seen. [ $+ [ $nick ] ] $true
}
I included flood protection which I think is mandatory for any text response.
I chose to use ".seen &" because & matches any word. So this will only be $true if $1 == .seen and $2 exists, but $3- doesn't.
.seen * means it will respond if someone puts anything behind .seen. Like: .seen nickname more text following.
You could also check if the nickname is on the channel as well.
if ($2 ison $chan) { msg $chan $2 was last seen $read(text.txt) }
I hope this helps.