This is Perl module Sub::Spy. INSTALLATION Install cpanm (App::cpanminus) and then run the following command to install Sub::Spy: $ cpanm Sub::Spy If you get an archive of this distribution, unpack it and build it as per the usual: $ tar xzf Sub-Spy-$version.tar.gz $ cd Sub-Spy-$version $ perl Makefile.PL $ make && make test Then install it: $ make install DOCUMENTATION Sub::Spy documentation is available as in POD. So you can do: $ perldoc Sub::Spy to read the documentation online with your favorite pager. LICENSE AND COPYRIGHT Copyright (c) 2011, Naosuke Yokoe. All rights reserved. This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.