This is Perl module HTML::Selector::XPath.
INSTALLATION
HTML::Selector::XPath installation is straightforward. If your CPAN shell is set up,
you should just be able to do
    % cpan HTML::Selector::XPath
Download it, unpack it, then build it as per the usual:
    % perl Makefile.PL
    % make && make test
Then install it:
    % make install
DOCUMENTATION
HTML::Selector::XPath documentation is available as in POD. So you can do:
    % perldoc HTML::Selector::XPath
to read the documentation online with your favorite pager.
Tatsuhiko Miyagawa