I was an electrician 20 years ago. We used to cut into PVC with a string but it was done when the pipe was empty.
My nephew is now working with PVC for fiber. He said that they cut into a pipe they thought was empty and it turned out it contained a fiber optics cable.
I was just wondering if you could wrap a string around a PVC pipe and keep tension on the spool and drive the cutting with an electric drill pulling the string?
I wonder how much success you could have in scoring around the pipe enough to break it in case it is not empty.