With "ol' procedural code" do you mean collections of functions in .pl files or standalone scripts? If you mean the first, then you can do normal Test::* tests, just require the file instead use'ing it. In the second case you may consider to convert the script into a hybrid script/module --- this is not too hard, just move the running part below a return 1 if caller; line. Now you can require the file and test the subroutines in it without running the script. If you don't have subroutines at all, then you can still check for side effects (e.g. created or changed files, or screen output). If the script is interactive, then you could consider to use Expect.pm.