Heres how I would do it with wxTextEntryDialog

sub add_alert {
    my ($self, $event) = @_;

#~  my $md = MyDialog->new(my $frame_1);
#~     $md->ShowModal();


    my $dialog = Wx::TextEntryDialog->new(
        $self,
        "Enter some text",
        "Wx::TextEntryDialog sample",
        9, # "I am a default value"
    );

    if ( $dialog->ShowModal == Wx::wxID_OK() ) { 
        unshift @numbers, $dialog->GetValue;
        $self->{text_ctrl_1}->SetLabel("The button @numbers");
    }

    $dialog->Destroy;

}
[download]