gistfile1.PL

# app.pl
use Dancer;

use MyApp::Forum;
use MyApp:Home;

dance;

# lib/MyApp/Forum.pm
package MyApp::Forum;
use Dancer ':syntax';

prefix '/forum';

get '/hello' => sub {
    # this is /forum/hello
};

# lib/MyApp/Home
package MyApp::Home;
use Dancer ':syntax';

prefix undef; # means root

get '/hello' => sub {
    # this is /hello
};