YAML: YAML Ain't Markup Language is a text format that provides hierarchical data structures similar to JSON, but it is especially human readable.

It can be used for data serialization, though probbaly it is most often used for hierarchical configuration files.

YAML format allows the user to have key-value pair and list data structures.

Plenty of languages have YAML reader and write libraries.

In Perl the following libraries exist:

Other articles about YAML

YAML vs YAML::XS inconsistencies (YAML::Syck and YAML::Tiny too)