In many cases, the site with SSO sets session cookies to keep track of authenticated sessios. Please try enabling cookie jars for LWP::Useragent, to store cookies either by adding

$ua->cookie_jar({ file => "$ENV{HOME}/.cookies.txt" });
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or

  require HTTP::Cookies;
  $ua->cookie_jar(HTTP::Cookies->new(file => "$ENV{HOME}/.cookies.txt"
+));
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or even

  $ua->cookie_jar({}); #this will store cookie in memory. Not in file
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to your code. Enable cookie jar before you send the request.

Hope this helps.

--VC