Perl's 20-year source code history for Perl 5 has been transitioned from Perforce to Git, with a mirror repository set up on GitHub to facilitate collaboration among developers. Spearheaded by Sam Vilain, this monumental project involved more than a year of effort to create a unified repository that includes every change to Perl, integrating data from Perforce, snapshot releases, mailing list archives, and patch sets from former release engineers. The GitHub repository is automatically updated every hour, offering a platform for developers to fork and contribute to the Perl project.