I am somewhat surprised that a programmer who was unaware of arrays in Perl managed to have tests. But then again, he managed to implement their own version of arrays, maybe he came up with the concept of software testing by himself :-P
It sounds more like the refactoring started with creating tests for the old code base. We do this with our legacy code base, too, sometimes. Of course, it’s always the high risk code of an application that‘s never been accompanied by automatic tests.
I am somewhat surprised that a programmer who was unaware of arrays in Perl managed to have tests. But then again, he managed to implement their own version of arrays, maybe he came up with the concept of software testing by himself :-P