This is the Perl distribution App-txtnix.
Installing App-txtnix is straightforward.
If you just want to run txtnix as easy as possible, you can always get the latest version at https://mdom.github.io/txtnix as dependency free prepackaged script.
If you have cpanm, you only need one line:
% cpanm App::txtnix
If you are installing into a system-wide directory, you may need to pass the "-S" flag to cpanm, which uses sudo to install the module:
% cpanm -S App::txtnix
Alternatively, if your CPAN shell is set up, you should just be able to do:
% cpan App::txtnix
As a last resort, you can manually install it. Download the tarball, untar it, then build it:
% perl Makefile.PL % make && make test
Then install it:
% make install
If you are installing into a system-wide directory, you may need to run:
% sudo make install
App-txtnix documentation is available as POD. You can run perldoc from a shell to read the documentation:
% perldoc txtnix