I think the best place to start is "Requirements Gathering".

Altho' perl can most definately do what you want, it may not be the best tool for you.

What are the goals of the resedign? just saying improved maintaince is not really enuff... what you need to do is start at the top, get agreed goals, and break down the project pieve (pun intended) by piece into smaller chunks.

For each small chunk, you can say it will take me 2-3 weeks to complete a production quality application or peice. From this data you can quantify to management how long it will take, and you can "Manage their expectations (tm)", which is always a good thing.

So, in short

Just wondering if anyone could advise me on suitable ways of developing...

Planning.