Once you copy the tree into the new environment (maintaining a copy of the original of course), you can run

find . -name '*.pl' -print0 | xargs -0 perl -pi'.bak' -e 's=/usr/local
+/www/=/etc/www/=g'
[download]

This is one of the few parts of the job where having little or nothing in modules makes your job a little easier.

If you find breakage from this, you can go back and do it again with a more refined substitute, or do further such substitutes. It's a case of Perl helping Perl.

As others have said, Perl Medic is good. It has good, realisitc advice on strategies, as well as providing tools to help you do the work. Our sympathies are with you.