JSON::XS before version 4.04 for Perl has an integer buffer overflow causing a segfault when parsing crafted JSON, enabling denial-of-service attacks or other unspecified impact
add \0 (JSON::XS::false) and \1 (JSON::XS::true) mappings to JSON true and false.
add some more notes to shrink, as suggested by Alex Efros.
improve testsuite.
half the default nesting depth limit, to hopefully make it work on Freebsd (unfortunately, the cpan tester did not send me his report, so I cannot ask about the stack limit on fbsd).