use Tk;
my $mw = MainWindow->new;
my $suchbegriff;
Tk::grid($mw->Label(-text => "Suchbegriff:"),
     my $e = $mw->Entry(-textvariable => \$suchbegriff),
     -sticky => "w");
$e->bind("<Return>" => sub { $mw->destroy });
MainLoop;

warn "Nun mach was mit <$suchbegriff>";