Perl Medic: Transforming Legacy Code

Chapter 7. Upgrading (Plastic Surgery)

“When we inherit property, it does not occur to us to throw it away, even when we do not want it.”

— Mark Twain, A Connecticut Yankee in King Arthur’s Court

Perl has remained extraordinarily backward compatible. The vast majority of programs written for Perl 4.018 will work identically on Perl 5.8.3. Thanks to the zealous efforts of a group affectionately—or otherwise—called the “backward compatibility police,” only a handful of changes were made during that decade that could change the behavior of existing code.¹

1. This will not be the case with Perl 6, however. The developers concluded that backward compatibility ...