If you want to use curl or net-http/open-uri to access https resources, you will often (always?) get an error, because they don't have the large number of root certificates installed that web browsers have.
You can manually install the root certs, but first you have to get them from somewhere. This article gives a nice description of how to do that. The source of the cert files it points to is hosted by the curl project, who kindly provide it in the .pem format.
problem: Sadly, ironically, and comically, it's not possible to access that file via https! Luckily, the awesome curl project does provide us with the script that they use to produce the file, so we can do it securely ourselves. Here's how.
git clone https://github.com/bagder/curl.git
my $url = 'http://mxr.mozilla.org/mozilla/source/security/nss/lib/ckfw/builtins/certdata.txt?raw=1';
my $url = 'https://mxr.mozilla.org/mozilla/source/security/nss/lib/ckfw/builtins/certdata.txt?raw=1';