OBJECTNAME_Eventname

##</code><code>##

    sub Button1_Click {
        # ...do something...
    }

##</code><code>##

sub Button1_Click { ... }

$main->AddButton(
  -name => 'Button1',
  ...,
);

##</code><code>##

$main->AddButton(
  -name => 'Button1',
  -onClick => sub { ... },
  ...,
);