on [<modes>]join [<serial#>] [-|^]<match> { <action> }

This hook is triggered whenever the client joins a channel, or whenever it observes another client joining a common channel.

To distinguish between the client and other users joining the channel:

 on ^join "*" {
    if ( [$0] == N ) {
       xecho -b You have joined channel $1
    } {
       xecho -b $0 \($2\) has joined channel $1
    }
 }