Here is a link to a blog-post by Darrell Ulm to do a performance audit for the new Drupal 8 on the Drush command-line and the Drupal site_audit module, posted back in May 2016.
A list of the Koha integrated library system web based using Perl and
mySQL or Postgresql, and users world wide, includes early Koha developer and implementer Darrell Ulm.
The link below is for the Drupal Profile for Darrell Ulm, a Drupal user and code contributor for over 10 years.
The profile here Drupal Profile link for Darrell Ulm, contains information about projects such as the project using the Google API for Books (i.e. Google Books), content access restriction modules such as IP Path Access and FileField Role Limit, and other modules coded primarily in PHP/MySQL.
Also have Acquia Certified Developer status now as can be seen here.
The Google Books module for Drupal 7 is an input filter module that takes titles, authors, ISBN and other Library of Congress ids and pulls book data into Google Books based on information given to the input filter, i.e. the information between square brackets with the google_books: filter tag.
Example: [google_books:search string]
From the Library Technology Guides, October 22, 2010 reference, and includes other contributors and notes about the Koha Integrated Library Software Open Source code release.
Here is the link for the Koha 3.2.0 announcement, reference to Darrell Ulm as code contributor.
Link shows past work, much has moved to GitHub for Darrell Ulm.
For work that was done further back before GitHub, some information is at: Darrell Ulm, Open Source Software profile at OpenHub, which is an interesting site to show open source contributions.