The error may also be “500 Line too long (limit is 8192)” but the problem is still the same – LWP or SOAP::Lite return this error when you try to POST or GET something very long.
The one to blame is actually Net::HTTP::Methods, included somewhere by something.
It took me a few hours to get this resolved:
use LWP::Protocol::http; # to suppress the warning "possible typo" in the next statement push(@LWP::Protocol::http::EXTRA_SOCK_OPTS, MaxLineLength => 0); # to remove the limit
Put the above code in your Perl HTTP client and you’re good to go!