Here is the answer: I am using the latest version of gnupg, but I need to use the interface version 0.44 of gnupg. I reinstalled gnupg.
Then no compilation errors were found. I can sign my message. but cannot send request. The problem is that I did not install the LWP :: Protocol :: Https module, which is used by "Useragent" to send the request. (I found out that I did not install the module, while maintaining simple print instructions that showed a problem that LWP :: Protocol :: Https was not found). So I installed the LWP :: Protocol :: Https module through cpan. And I am ready to go. Finally, everything is installed :-)
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