On part
The on PART events trigger when a user parts a channel.
on <level>:PART:<#[,#]>:<commands>
The part message is saved in $1-.
Note that this event also triggers when you part a channel.
Example
on *:PART:#: {
echo $chan $nick has just parted $chan (reason: $iif($1-,$1-,None) $+ ).
}
This example reacts on every part in a channel you are in and echos it to this channel.
on me:*:PART:#: {
echo -s I have just parted $chan
}
This example will react on you parting a channel and echo it to your Status Window. Note that is no mistake, the prefix is "me:".
See Also
To react on joins, take a look at the On join event.
The On quit event is triggered when someone quits IRC.