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

This hook is triggered whenever the client observes a nickname change. It only hooks once per nick change, not once per channel.

To distinguish the client from another user:

 on ^nickname "*" {
    if ( [$0] == N ) {
       xecho -b Your nickname is now $1
    } {
       xecho -b $0 has changed nicks to $1
    }
 }