-----------------------------596088922920
Content-Disposition: form-data; name="Filedata"; filename="mypic.gif"
Content-Type: image/gif

GIF87aX#  *shorted*  ¡§\
-----------------------------596088922920
Content-Disposition: form-data; name="session"

92384729384792384729384729384
-----------------------------596088922920
Content-Disposition: form-data; name="method"

put
-----------------------------596088922920--

use WWW::Mechanize;
$agent = WWW::Mechanize->new( cookie_jar => {} );
  $agent->post('http://www.kleiderkreisel.de/photo/ajax_photo_action',
    [
        "Filedata" => ['mypic.gif' => 'C:\Pics\mypic.gif'],
        'session' => '92384729384792384729384729384',
        'method' => 'put'
    ]);