This is Perl module Sub::Attribute.

INSTALLATION

Sub::Attribute installation is straightforward. If your CPAN shell is set up,
you should just be able to do

   $ cpan Sub::Attribute

Download it, unpack it, then build it as per the usual:

   $ perl Makefile.PL
   $ make && make test

Then install it:

   $ make install

DOCUMENTATION

Sub::Attribute documentation is available as in POD. So you can do:

   $ perldoc Sub::Attribute

to read the documentation online with your favorite pager.

Goro Fuji (gfx)