It's needed for an investigation into differences between different environments of the same system, e.g. devt. versus QA. The time to approve such porting would exceed acceptable limits for completion of the work, given that this work can be achieved without any porting and that it turns out two lines added to the OP code would make it algorithmically identical to Algorithm::Diff. I'll update the OP with that for clarity. I note also that Text::Diff uses the same algorithm.

I could find no reference to Algorithm::Diff3 on CPAN.