It seems like the target (Bauer Versand) requires JavaScript for the content to be rendered properly. Without JavaScript, you just get the note:
Um Ihnen den Online-Einkauf so angenehm wie möglich zu machen, arbeiten wir mit der neuesten Technik.
Aus diesem Grund sind unsere Seiten für JavaScript-fähige Browser optimiert.
Leider unterstützt Ihr Browser zur Zeit nicht diese Funktion.
Damit auch Sie von den vielen Vorteilen profitieren können, müssen Sie in Ihren Einstellungen die Funktion "JavaScript/ActiveScripting" aktivieren.

In short, it tells you to activate JavaScript.

As for WWW::Mechanize to follow the redirect link, just say 

my $mech = WWW::Mechanize->new();
my $response = $mech->get( $url );
$mech->follow_link( n => 1 ); # this is the one in the META tag
my $html = $mech->content;
...

[download]

Since you use Firefox, you might want to look at JavaScript::SpiderMonkey to evaluate JavaScript. Some time ago, I wrote Re: Handling Javascript with LWP::UserAgent which might serve as an example.

--shmem 

_($_=" "x(1<<5)."?\n".q·/)Oo.  G°\        /
                              /\_¯/(q    /
----------------------------  \__(m.====·.(_("always off the crowd"))."·
");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}

In reply to Re: WWW::Mechanize or WWW::Selenium with server side redirect by shmem
in thread WWW::Mechanize or WWW::Selenium with javascript redirect by tphyahoo

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.