Example code for Route/FastRoute config...

base-routing.php

<?php

return [
    'demo' => [
        'prefix' => '/demo',
        'routes' => require realpath(__DIR__ . '/Demo/routing.php'),
    ],
    'security' => [
        'prefix' => '',
        'routes' => require realpath(__DIR__ . '/Security/routing.php'),
    ],
    'separated_routes' => require realpath(__DIR__ . '/SeparatedRoutesDemo/Resource/routing.php'),
];

RouteCollection.php

<?php

/**
 * This is simplistic code to illustrate how routing config files could be implemented.
 */

    public function addRoutesFromConfig(
        array $routes = [],
        $namedRoutes = false,
        Strategy\StrategyInterface $strategy = null
    ) {
        foreach ($modules as $moduleName => $moduleConfig) {
    
            if (true === isset($moduleConfig['routes'])) {
                foreach ($moduleConfig['routes'] as $routeName => $routeConfig) {
                    $route = sprintf('%s%s', $moduleConfig['prefix'], $routeConfig['pattern']);
                    $this->addRoute($method, $route, $handler, $name);
                }
            } else {
                foreach ($moduleConfig as $moduleName => $moduleConfig) {
                    foreach($moduleConfig['routes'] as $routeName => $routeConfig) {
                        $route = sprintf('%s%s', $moduleConfig['prefix'], $routeConfig['pattern']);
                        $this->addRoute($method, $route, $handler, $name);
                    }
                }
            }   
        }
    }

src_Demo_Routing_routing.php

<?php

return [
    'demo_one' => [
        'pattern'    => '/hello/{name:word}',
        'handler' => 'Demo\Controller\DemoController::helloPerson',
        'method'     => 'GET',
    ],
    'demo_two' => [
        'pattern'    => '/bye/{name:word}',
        'handler' => 'Demo\Controller\DemoController::byePerson',
        'method'     => 'GET',
    ],
];

src_Security_Routing_routing.php

<?php

return [
    'login' => [
        'pattern'    => '/login',
        'handler' => 'Security\Controller\AuthenticationController::login',
        'method'     => 'POST',
    ],
    'logout' => [
        'pattern'    => '/logout',
        'handler' => 'Security\Controller\AuthenticationController::logout',
        'method'     => 'POST',
    ],
];

src_SeparatedRoutesDemo_Routing_one.php

<?php

return [
	'route_one' => [
	    'pattern'    => '/route/first',
	    'handler' => 'One\Controller\OneController::first',
	    'method'     => 'GET',
	],
	'route_two' => [
	    'pattern'    => '/route/second',
	    'handler' => 'One\Controller\OneController::second',
	    'method'     => 'POST',
	],
];

src_SeparatedRoutesDemo_Routing_routing.php

<?php

return [
    'one' => [
        'prefix' => '/one',
        'routes' => require realpath(__DIR__ . '/one.php'),
    ],
    'two' => [
        'prefix' => '/two',
        'routes' => require realpath(__DIR__ . '/two.php'),
    ]
];

src_SeparatedRoutesDemo_Routing_two.php

<?php

return [
	'route_one' => [
	    'pattern'    => '/route/first',
	    'handler' => 'One\Controller\OneController::first',
	    'method'     => 'GET',
	],
	'route_two' => [
	    'pattern'    => '/route/second',
	    'handler' => 'One\Controller\OneController::second',
	    'method'     => 'POST',
	],
];