Since Mule 3.3 the Mule Expression Language (MEL) has been the default scripting language for expressions in Mule. It is very powerful and based on the MVEL language (note you can also use JavaScript, Groovy, Python and Ruby). MEL provides a very easy way to access the current message in a flow, write conditional filters and perform content based routing. The MEL Cheat Sheet, gives you an overview of the commands you can use.
Other Resources
- Mule Expression Langauge Reference Guide
- Using Mule Expressions
