The plugin is only catching the highlights and private message to print them
into the file ~/.irssi/fnotify. To send notifications, we will use the
libnotify library which provide the notify-send command. To call that
command into our Perl script, we will use the system function.
To make it work, you will probably need to install libnotify (which may be
there if you’re using Gnome) and Perl (which may be installed with irssi).
You can find the modify script here.