A complex variable can be defined as anything that is not a simple string or a number. For example, a Local File can be considered a complex variable with various attributes in it such as the name, path, extension, size, etc. To retrieve the attributes of a complex variable use the following variable reference syntax.
${variableName:attributeName}.
The colon (:) separates the variable from the attribute.
Variables and their attributes are case sensitive. For example, ${file:lastModifiedDate} returns the name of the file and ${file:lastmodifieddate} will generate an error with the message: Variable Not Found.