From what I know an http authentication can not be done with a certificate. It is done with user credentials (username/passwords) protected by an encrypted communication (https).
No, HTTPS authentication can be done with a certificate. However I am not sure if LWP allows this. And yes SSL_ca_file is possible incorrect option. Documentation for this stuff should be somewhere here http://search.cpan.org/perldoc?IO%3A%3ASocket%3A%3ASSL

In reply to Re^2: LWP UserAgent - Sending Client Certificate connect to remote host by vsespb
in thread LWP UserAgent - Sending Client Certificate connect to remote host by kabachaa

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