Mule Expression Language (MEL) is a flexible tool that can be used to evaluate various types of expressions, including constants, simple operands, and operations. In Mule 3, it is necessary to learn both MEL and DataWeave. This reference page provides information on MEL features such as operators, literals, and functions. It is assumed that the reader is already familiar with MEL. MEL also does not have direct support for JSON, but the json-to-object-transformer can be used for parsing JSON data. Additionally, there are date and time functions available in MEL.