libjson-xs-perl 2.320-1build1 (amd64 binary) in ubuntu precise

 JSON::XS is a module for manipulating data stored in the JavaScript Object
 Notation (JSON) serialization format (defined in RFC 4627), which serves as
 an alternative to XML.
 .
 This C/XS-accelerated JSON implementation confers significant performance
 gains if available. After installing this package, any code using the JSON
 module (see libjson-perl) will automagically benefit from this.