How can I speed up my Perl program?

Question

This is really two questions, but they are so similar, and to keep it simple, I figured I'd just roll them together:

• Firstly: Given an established Perl project, what are some decent ways to speed it up beyond just plain in-code optimization?

• Secondly: When writing a program from scratch in Perl, what are some good ways to greatly improve performance?

For the first question, imagine you are handed a decently written project and you need to improve performance, but you can't seem to get much of a gain through refactoring/optimization. What would you do to speed it up in this case short of rewriting it in something like C?

Please stay away from general optimization techniques unless they are Perl specific.

I asked this about Python earlier, and I figured it might be good to do it for other languages (I'm especially curious if there are corollaries to psycho and pyrex for Perl).

Answer 1

Please remember the rules of Optimization Club:

1. The first rule of Optimization Club is, you do not Optimize.
2. The second rule of Optimization Club is, you do not Optimize without measuring.
3. If your app is running faster than the underlying transport protocol, the optimization is over.
4. One factor at a time.
5. No marketroids, no marketroid schedules.
6. Testing will go on as long as it has to.
7. If this is your first night at Optimization Club, you have to write a test case.

So, assuming you actually have working code, run your program under Devel::NYTProf.

Find the bottlenecks. Then come back here to tell us what they are.

If you don't have working code, get it working first. The single biggest optimization you will ever make is going from non-working to working.