This makes me think that the PHP CPAN module is a good thing in this regard, and that frameworks for transition may be better than code converters.
In general rewriting apps in another language means rethinking everything because there are all sorts of things that just don't quite match between apps. Something to ease the transition might be very good. So for example, despite my skepticism I think the following could be helpful
- Boilerplate converters. Take a PHP object definition and turn it into a basic Moo or Moose definition. Don't port the methods, just the boilerplate.
- Bridging type classes. The ability to have a PHP Array inside your Perl code may ease the transition quite a bit.
- Web application frameworks written with conversion in mind.
These strike me as both easier and less work than a full-blown code converter but also provide all the basic infrastructure to allow a human to conversion relatively quickly and easily...