|P is for Practical|
I have not ever used or developed VOIP software, but I will try to help you get passed the initial obstacles of starting your project with general advice.
As others said, there are numerous open-source packages for what you want to do. Start with installing their "server" on your computer. Most likely, using Linux will make these installations easier. I had very hard time keeping old Mac hardware, which limits OS version, up-to-date with new applications. Can you afford a Raspberry? Or, I had success installing modern linux on 15-year old laptops. There are strip-down versions of Linux specifically for running on old hardware. There are resources on how to install voip servers (mumble for example) on rapsberry (https://pimylifeup.com/raspberry-pi-mumble-server/) or Linux (https://wiki.mumble.info/wiki/Installing_Mumble).
Once you are successful with the server, experiment with connecting a ready-made, open-source voip client to it. Each voip software will offer some kind of C/C++/Java API for creating your own client. So, if you are successful with connecting with 3rd-party client, it is now time to create your own client. Nothing fancy, avoid GUI. Make a CLI program, following tutorials, on how to place a call, for example. All 3 languages C/C++/Java are supported by the fabulous Inline module and this will be the easiest way to "bind" your client with Perl.
If you have your own SIP server then you can use Net::SIP as has already been suggested to contact it. Linphone also offers an API for writing apps for it.
You have quite a few options, it seems.
If I may suggest: use linux whenever possible, it will make your life easier and will empower you and your compatriots. And btw I can think of something worse than a "3rd-world country": a developed country with people of "3rd-world" mentality.
In reply to Re: Is a Perl Skype-like VoIP connection possible?