Another "been there" to extremely
My first big Perl project was fairly complicated and then I went to other things. I had left some code in that didn't do anything but generate a lot of data. The data interpretor wasn't done. There were other parts that were badly designed, etc...
The person that took over me, didn't do anything to the code and forbid his co-worker to touch it.
I wound up back in that area. Ouch. Nothing worse than looking at your old code. It still ran, but some of the parsing wasn't happening correctly and some errors were happenning, but they were stealth errors.
Sometimes it just looks like it's running.