The directory book contains the LaTeX sources needed to compile the book.
To recompile it, run the following command within the directory:
make
This command will create the directory tmpDir where you'll find the PDF (thinkperl6.pdf)
alonside other intermediate files created during the compilation process.
To move the created pdf to the directory PDF in the root directory, run:
make pdf
To remove tmpDir, run:
make clean
Note: The chances of a successful compilation increase if you have an almost complete installation of a recent TeX Live distribution.
Also note that a PDF version is available (https://github.com/LaurentRosenfeld/thinkperl6/tree/master/PDF).