New post on altering the source of #guix packages using the substitute* procedure.
It searches through files using a #guile regular expression and replaces it with the specified text.
This is the most common change that packages make - substitute* is used 9500 times!
Common uses are altering test requirements, or slackening library dependencies.
https://www.futurile.net/2026/04/18/guix-package-source-alterations-using-substitute/
Post covers the procedures uses, and then a tour through different examples from the Guix archive!