Auto-join all currently open channels in Irssi

Is there a way to tell Irssi that I want to auto-join all of the channels that are currently open?

I want something like:

/channel add -auto <all my currently open channels>
/save

I found the answer here:

/alias addallchannels script exec foreach my \$channel (Irssi::channels()) { Irssi::command("channel add -auto \$channel->{name} \$channel->{server}->{tag} \$channel->{key}")\;}

Followed by:

/addallchannels
/save