I was involved in migration of about 500k locs of Perl code to PHP. First we tried to rewrite (refactor) project to make code clearer, but it becomes just copy

I was involved in migration of about 500k locs of Perl code to PHP. First we tried to rewrite (refactor) project to make code clearer, but it becomes just copy-paste, without real rewriting. So have chosen to migrate to PHP, which was mature enough at that time (PHP 5 already appears, but chosen 4), and in about year, testers said, it work. This is ERP like platform, on LAMP stack, and fortunately, used Perl 3 practices and very old framework, so performance mostly depends on database speed. Most important where to make complete enough test suite (mostly used tests just from Perl version), and than just do classic loop write-test-fix...