That's not really going to give you a taste for what it's like to "do" COBOL in a real-world scenario. Realistically, no one is running COBOL on a modern Linux. They're running it on something like z/OS and there is so much utterly bizarre and incredibly tedious stuff you have to deal with on those mainframe OS's that you'll run away screaming. And that's not even mentioning the code itself, written over several decades and likely not well documented.

When I worked at IBM not TOO long ago there were times when I had to fix a bug in WebSphere that only manifested on z/OS or zLinux and those were hands down the hardest bugs to fix. And that was a relatively modern codebase, by mainframe standards.

Open-cobol works, but be aware that it translates your source to C and then compiles that. If that doesn't matter to you, great!

There's also tiny-cobol[0], but the project is dead and it only targets x86-32.

[0] http://tiny-cobol.sourceforge.net/