The perl module LWP::UserAgent (at version 6.08) does not play well with custom CA certificates and most online resources seem to be outdated. Two notes on that (which may or may not apply to non-Debian systems as well):

• If a certificate failed verification, you will not get a nice error message. Temporary workaround: sudo mv /usr/share/perl/5.20.1/IO/Socket/IP.pm{,_} (and then later sudo mv /usr/share/perl/5.20.1/IO/Socket/IP.pm{,_})
• LWP::UserAgent does not support custom certificates installed with update-ca-certificates. You'll need HTTPS_CA_FILE=/etc/ssl/certs/ca-certificates.crt in your environment.