It’s not just the actually copying of source code that’s protected, but also the structure, sequence, and organisation of the computer software. This stops third parties from being able to just change the source code slightly and end up with the same outcome as with your software and not count that as copyright infringement.
If your software is registered, you could be entitled to significant compensation payments for your works if they are infringed upon. If you suspect that this is the case, you should gather a copy of the infringing work as well as a copy of the registered version of your own work, and any other dated documents proving your work’s registration. As well as the option of fining the infringers, there are other remedies such as temporary and final injunction relief to make sure no other infringement can happen in the future. The costs and attorneys’ fees are sometimes enough to make the infringer come to a settlement more quickly before the costs rise and this means you won’t have the hassle of going through the courts.
Note that copyright protection is only valid for the version of the software that you registered, so every time you update the software you need to register the new version with the IPO.