- Break the code up into manageable chunks. If it's "well-documented", 10-1 it's already this way.
- Find a bug in one manageable chunk.
- Write a test for it using Test::More.
- Make sure the test fails.
- Because the code has to be in this manageable chunk (no more than 1-5k lines), it shouldn't be hard to zero in on the problem.
- Fix the problem.
- Rerun the test and see it pass.
You now have the beginnings of a test suite. Never remove a test, unless the requirements change. Every test should always pass, unless you wrote it because you're changing something, in which case it should fail until you finish changing it.
That's it. Nothing to it.
- In general, if you think something isn't in Perl, try it out, because it usually is. :-)
- "What is the sound of Perl? Is it not the sound of a wall that people have stopped banging their heads against?"