This works fine, until my $responseText = $latin2->decode($response->content); where decode seems to do nothing at all

It would help to know which characters are misinterpreted in what way.

Before this line, try

use Data::Dumper;
$Data::Dumper::Useqq = 1;
print Dumper $response->content
[download]

and past relevant parts of the output, along with your interpretation which characters those should be.