sub do_top {
    if ( !Exists($tl) ) {
        $tl = $mw->Toplevel;
        $tl->title('Help');
        $tl->geometry("1000x700");

        my $frame = $tl->Frame()->pack;
        my $lab   = $tl->Label()->pack;
        my $ent   = $tl->Entry()->pack;
        
#### ANONYMOUS SUB , ANONYMOUS CLOSURE, 
#### CLOSED OVER LEXICAL $text
#### $text is lexical to if {} block in do_top
        my $text = $tl->Scrolled('Text');
        my $push_button2 = sub {
            $text->insert( 'end', "You pushed button2\n" );
        };
        $tl->Button( -text => 'Exit', -command => sub { $tl->destroy; } )->pack;
        $tl->Button( -text => 'Open File1', -command => $push_button2  )->pack;

        $text->pack();

    } else {
        $tl->deiconify;
        $tl->raise;
    }
}