flooph

https://github.com/Phrogz/Flooph

Flooph is a Ruby library designed to let you take code from (possibly-malicious) users and evaluate it safely. Instead of evaluating arbitrary Ruby code (or JavaScript, or any other interpreter), it specifies a custom 'language', with its own parser and evaluation. Flooph provides four core pieces of functionality: * A simple syntax for specifying key/value pairs (much like a Ruby Hash literal). * A simple template language that supports conditional content and injecting content. * Standalone functionality for evaluating conditional expressions based on the key/values (also used in the templates). * Standalone functionality for evaluating value expressions based on the key/values (also used in the templates).