Re: [xml-dev] parsing markup with Perl

[Michael Kay <mike@saxonica.com>]

They had unreadable code and it was driving them into the ground. My takeaway was that Perl as it stood then required infeasibly much commenting to be maintainable

My only encounter with Perl was equally negative. I was called in as a consultant to rescue a system that had serious performance problems (like response times of two minutes for customers checking the balance on their accounts). It all turned out to be due to one module, written in Perl, which was doing regex-based transformations on XHTML pages. It took a while to work out what the 500 lines of Perl was trying to do, but in the end we rewrote it (using Java DOM, I believe - the project wasn't a good place right then for anything innovative) and solved all the problems at a stroke.

Regular expressions seem to have two problems. The first is that they are unreadable. Anything but the simplest regexes are impenetrable to anyone reading the code, and often to the person writing it, which is why debugging is so hard. The second is that performance is highly unpredictable except to people who really understand the technology extremely well. 

I think we should treat Perl a bit like certain pesticides; something you're only allowed to use if you've been through the right training courses and have acquired a license, which has to be renewed every year by passing exams.

Michael Kay

Saxonica