500 Missing newline after chunk data: '     <ul>'

#!/usr/bin/perl -w

use strict;
use warnings;
use WWW::Mechanize;

my $htmlInput = ">ENSP00000260327 [Homo sapiens]\nMKLRTRKASQQSSPIQTQRTARAKRKYSEVDDSLPSGGE\n>ENSPTRP00000011989 [Pan trogldoytes]\nMRLRTRKASQ\n";
my $mech = WWW::Mechanize->new();
$mech->get('http://www.ebi.ac.uk/Tools/clustalw2/index.html');
$mech->submit_form(
        form_name => 'form3',
        fields => {'sequence' => $htmlInput}            
);
my $content = $mech->response()->content;
print "$content\n";