There are four ways to let Gtk2::Builder do the signal connecting work for you:

$builder->connect_signals ($user_data)

When invoked like this, Gtk2::Builder will connect signals to functions in the calling package. The callback names are specified in the UI description.

$builder->connect_signals ($user_data, $package)

When invoked like this, Gtk2::Builder will connect signals to functions in the package $package.

$builder->connect_signals ($user_data, $object)

When invoked like this, Gtk2::Builder will connect signals to method calls against the object $object.

$builder->connect_signals ($user_data, %handlers)

When invoked like this, %handlers is used as a mapping from handler names to code references.