sub irc_public {
     my ($sender, $who, $where, $what) = @_[SENDER, ARG0 .. ARG2];
     my $nick = ( split /!/, $who )[0];
     my $channel = $where->[0];

     if ( my ($rot13) = $what =~ /^rot13 (.+)/ ) {
         $rot13 =~ tr[a-zA-Z][n-za-mN-ZA-M];
         $irc->yield( privmsg => $channel => "$nick: $rot13" );
     }
     return;
 }