To be clear, all the code works well in that it does everything it is supposed to do consistently and within an acceptable time ... I do have test environments so I would not have to break the code whilst it is in production!

What is the current state of your code?

• Roughly how many lines of code? Thousands? Millions?
• Is it designed as a set of (loosely coupled) cohesive modules?
• How well does it do information hiding?
• Is it designed so that components can be easily tested in isolation?
• How happy are you with your current interfaces?
• Are you following a consistent error handling strategy? What is it?
• Do you have unit tests? Do they test boundary conditions? Errors and exceptions?
• Do you know what percentage of your code is covered by tests? (e.g. using Devel::Cover)

The ideal is to gradually improve your code, one module at a time, always keeping a working system. Typically you would add use strict only when you need to change a module anyway and so need to retest it.

Re when/if to rewrite working legacy code, I keep a long list of previous PM discussions on that tricky topic at: Re: Strategies for maintenance of horrible code? (Legacy Code References)