As always when automating things and finding different behaviour between other programs, you need to find out where exactly the differences lie. My first guess would be that you're not sending the expected Referer (sic) header. But only a network trace like the HTTP Live Headers or Wireshark produce can tell for sure.

Maybe WWW::Mechanize already works for you as it mimics browser behaviour far closer than LWP::UserAgent does of itself.

I traced the headers with a firefox plugin for the requested page:

GET /livelink_en/livelink/fetch/2000/customview.html?func=llworkspace 
+HTTP/1.1

Host: tsi-myworkroom.telekom.de

User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8.1.6) Gecko/
+20070725 Firefox/2.0.0.6

Accept: text/xml,application/xml,application/xhtml+xml,text/html;q=0.9
+,text/plain;q=0.8,image/png,*/*;q=0.5

Accept-Language: en-us,en;q=0.5

Accept-Encoding: gzip,deflate

Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7

Keep-Alive: 300

Connection: keep-alive

Cookie: LLCookie=vDF63XqtCC4%3D; LLTZCookie=0; SMSESSION=caPsWnnX9ytaP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; JSESSIONID
+=6809B0E13E9DEBF6265377F798EAD315; AtlasURLCookie=https%3A%2F%2Ftsi-m
+yworkroom.telekom.de%2Flivelink_en%2Flivelink%2Ffetch%2F2000%2Fcustom
+view.html%3Ffunc%3Dllworkspace

Cache-Control: max-age=0
[download]

nothing strange so far.. But I noticed something in the response header which is given back to the request of my perl script.

Connection: close
Date: Thu, 18 Oct 2007 10:44:48 GMT
Via: 1.1 G8NTQV01.bmbg01.telekom.de (Alteon iSD-SSL/3.1.6.2)
Server: Sun-ONE-Web-Server/6.1
Content-Type: text/html
Expires: -1
Client-Date: Thu, 18 Oct 2007 10:44:49 GMT
Client-Peer: 164.29.91.244:443
Client-Response-Num: 1
Client-SSL-Cert-Issuer: /C=DE/O=T-Systems Enterprise Services GmbH/OU=
+Trust Center Deutsche Telekom/CN=Deutsche Telekom CA 5
Client-SSL-Cert-Subject: /O=T-Systems CDS GmbH/OU=CS Unit 7/L=Bamberg/
+ST=Bayern/C=DE/CN=tsi-myworkroom.telekom.de
Client-SSL-Cipher: DES-CBC3-SHA
Client-SSL-Warning: Peer certificate not verified
Link: </livelink_ensupport/livelink.css>; rel="stylesheet"; type="text
+/css"
Refresh: 0; URL=/livelink_en/livelink/fetch/2000/customview.html?func=
+llworkspace
Set-Cookie: LLInProgress=; Expires=Sun, 01 Jan 1995 08:00:00 GMT; path
+=/livelink_en/
Set-Cookie: LLCookie=vDF63XqtCC4%3D; path=/livelink_en/
Set-Cookie: LLTZCookie=0; path=/livelink_en/
Title: Livelink - Redirection
[download]

It says "Client-SSL-Warning: Peer certificate not verified", could this be the reason? And what should I do next? thanks! dibucho

If you want to find out why FireFox and your program behave differently, look at the difference between the two network conversations. So far, you have only looked at the FireFox part of things. Now, also look at what your program sends and receives.

How else do you think you could figure out where the two differ?