# My memory of the gist of what's in the book, a few hours after having looked it up:
my $thing = do {
    if    ($cond1) { "Foo" }
    elsif ($cond2) { "Bar" }
    else           { "Baz" }
};

##</code><code>##

my $thing = do {
    ($cond1) ? "Foo" :
    ($cond2) ? "Bar" :
               "Baz";
};

##</code><code>##

my $thing = ($cond1) ? "Foo" : 
            ($cond2) ? "Bar" :
                       "Baz";

##</code><code>##

my $thing = do {
    my $rn = int(rand(6))+1;

    ($rn == 6) ? "Excellent roll"    :
    ($rn > 3)  ? "Pretty good roll." :
    ($rn == 1) ? "Lousy Roll"        :
                 "Meh.";
};

##</code><code>##

sub agent {
    my $self = shift;
    return $self->{_agent} //= do {
        require config;
        my $agent_args = $config::config{'agent_args'};
        require Agent;
        return Agent->new($agent_args);
    };
}