/usr/share/doc/ruby-gsl/examples/random/ is in ruby-gsl 2.1.0.3+dfsg1-1build1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/doc/ruby-gsl/examples/random/diffusion.rb
/usr/share/doc/ruby-gsl/examples/random/gaussian.rb
/usr/share/doc/ruby-gsl/examples/random/generator.rb
/usr/share/doc/ruby-gsl/examples/random/hdsobol.rb
/usr/share/doc/ruby-gsl/examples/random/poisson.rb
/usr/share/doc/ruby-gsl/examples/random/qrng.rb
/usr/share/doc/ruby-gsl/examples/random/randomwalk.rb
/usr/share/doc/ruby-gsl/examples/random/randomwalk2d.rb
/usr/share/doc/ruby-gsl/examples/random/rayleigh.rb
/usr/share/doc/ruby-gsl/examples/random/rng.rb
/usr/share/doc/ruby-gsl/examples/random/rngextra.rb