JSON (JavaScript Object Notation) is a simple data format. See to
http://www.json.org/ and RFC4627(http://www.ietf.org/rfc/rfc4627.txt).

This module converts Perl data structures to JSON and vice versa using either
JSON::XS or JSON::PP.

JSON::XS is the fastest and most proper JSON module on CPAN which must be
compiled and installed in your environment. JSON::PP is a pure-Perl module
which is bundled in this distribution and has a strong compatibility to
JSON::XS.

This module try to use JSON::XS by default and fail to it, use JSON::PP
instead. So its features completely depend on JSON::XS or JSON::PP.