Great advice!

I realize the code above is just a demo and not a full implementation, but just a note on coding and error handling as appropriate here. I'd rewrite some of the above like this:

eval {
    require $_;
    my $plugin = $_->new or die "failed to instantiate\n";
    $plugins{$pluginName} = $plugin;
} or logger("failed to load plugin: $@");
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Plugins can and will fail, so treat them with some skepticism :) -- this is actually a benefit of decoupling that you can afford to keep the main application running even if a plugin failed. In terms of development, if you expose a mechanism to rescan the plugin repository, you can reattempt to load a failing plugin without restarting your application. (Theoretically you could also implement plugin unload routines, but that's harder.)

Plugins are a great opportunity to use either interfaces or traits. Getting compile-time (or at least, plugin load-time) verification that it conforms to the plugin interface is nice.