This is protobuf-perlxs, a Perl/XS code generator for Google's Protocol
Buffers.  The generated Perl/XS code is meant to be compiled and linked
with the generated C++ code, and it provides the Perl developer with a
high performance interface to Protocol Buffer objects.

Each top-level message generates a Perl module, an XS source file, and
a typemap.  Each top-level enum generates a Perl module and an XS 
source file.  No typemap is needed for a top-level enum.

If the .proto file specifies a package name, the package name is
converted to a Perl package prefix like so:

file.proto
---------------------------
package foo.bar.baz;

message qux {
  ...
}

becomes (in Perl):

Qux.pm
---------------------------
package Foo::Bar::Baz::Qux;

Qux.xs
---------------------------
#include "file.pb.h"

MODULE = Foo::Bar::Baz::Qux  PACKAGE = Foo::Bar::Baz::Qux
PROTOTYPES: ENABLE

qux.typemap
---------------------------
::foo::bar::baz::qux * T_FOO_BAR_BAZ_QUX

The Perl/XS code generator assumes that the C++ code generator will
have been run on the same .proto files by the time the sources are to
be compiled.  It is possible to build a Makefile.PL that compiles the
generated C++ sources along with the generated XS sources, and it is
also possible (preferable, in fact) to compile the C++ sources into a
shared library separately, linking the compiled XS sources with this
shared library.  In both scenarios, the generated C++ headers need to
be present in the include path, as they are included by the XS source
files.