Because you're passing the url of the page the user requested when you mean to redirect to the login page.

Maybe $cgi->url(-base => 1) . '/login.html'?

In reply to Re^3: CGI error: "Invalid header value contains a newline not followed by whitespace" by ikegami
in thread CGI error: "Invalid header value contains a newline not followed by whitespace" by groengoen

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