I was super impressed by this paper, and I just had to try messing with it a bit. I found it because of this blog post at Hacker School.
Hopefully, this will be interesting to someone - it's nothing more than a start.
Here's a demo - the debian_package_file string is defined in demo.py.
# Extract groups of non-blank lines,
# Where the Section is 'non-free/web',
# Split into individual lines,
# Take the one that's the package name,
# And print it.
fishrob(debian_package_file) \
.x(r'(.+\n)+') \
.g(r'Section: non-free/web') \
.x(r'.+\n') \
.g(r'^Package:') \
.p()
# Should print:
# Package: album-data
# Package: album
Compare it to Pike's example on page 5 (adapted to Debian Package files):
x/(.+\n)+/ g/Section: non-free\/web/ x/.*\n/ g/Package/p
Keep being awesome, Hacker School!