#! /usr/bin/perl

use strict;
use warnings;
use Data::Dumper;
use HTML::TreeBuilder;

# meteoalarm.html contains the source of your link
open my $fh, q{<}, q{meteoalarm.html}
  or die qq{cant open file to read: $!\n};
  
my $content = do{local $/; <$fh>};
my $data = _parse_details($content);
print Dumper $data;

sub _parse_details {

    my $content =shift;
    my (%data);

    my $p = HTML::TreeBuilder->new_from_content(
      $content
    );

    $data{fullname} = $p->look_down(
      _tag => q{h1}
    )->as_text;

    my @warnbox_divs = $p->look_down(
      _tag  => q{div}, 
      class => qr/warnbox wb\d/
    );

    for my $div (@warnbox_divs) {

      my ($as_txt);

      my @info_divs = $div->look_down(
       _tag  => q{div}, 
       class => q{info}
      );

      $as_txt = $info_divs[0]->as_text;
      my ($from, $until) = 
        $as_txt =~ /valid from (.*) Until (.*)$/;

      $as_txt = $info_divs[1]->as_text;
      my ($warning, $level) = 
        $as_txt =~ /([^\s]+)\s+Awareness Level:\s+(.*)/;

      my $text = $div->look_down(
        _tag  => q{div}, 
        class => q{text}
      )->as_text;

      $data{warnings}{$warning} = {
        level => $level,
        from  => $from,
        until => $until,
        text  => $text,
      };

    }

    return \%data;
}
[download]

$VAR1 = {
  'warnings' => {
    'Wind ' => {
      'until' => '30.05.2010 22:00 CET ',
      'level' => 'Yellow  ',
      'text' => 'Allm㧬ich zunehmender S�wind mit .....',
      'from' => '30.05.2010 06:05 CET'
    },
    'Rain ' => {
      'until' => '01.06.2010 10:00 CET ',
      'level' => 'Orange  ',
      'text' => 'Zeitweise schauerartig verst㱫ter Dauerregen ....',
      'from' => '30.05.2010 07:17 CET'
    },
    'Thunderstorms ' => {
      'until' => '30.05.2010 15:00 CET ',
      'level' => 'Yellow  ',
      'text' => 'Loklae Gewitter. Dabei vereinzelt Sturmb�bis ....',
      'from' => '30.05.2010 13:30 CET'
    }
  },
  'fullname' => 'Weather warnings: Baden-Württemberg    '
};
[download]

Thanks wfsp for your code. I added your suggestion (slightly modified) to the original script.