sub rechnen {
    chomp (my ($c1, $c2) = ($eingabe->Contents, $eingabe2->Contents));
    my $output;
    while ($c1<=$c2) {
        my $f = (($c1 * 9)  /5 ) +32;
        my $k = $c1 + 273.15;
        $output .= "$c1\t$f\t$k\n";
        $c1+=10;
    }
    $ausgabe->Contents($output);
}