New in v5.4.0 Multi-valued variable attribute values are indicated with double round brackets around the variable name. This passes the complete list of values of a multi-valued variable to the attribute, rather than just the first value.

<$transclude $variable="myproc" items=((myvar))/>

This is the multi-valued counterpart to the Variable Attribute Values syntax <<var>>, which only returns the first value for backwards compatibility. The relationship mirrors the existing convention in filter operands where <var> returns a single value and (var) returns all values.

Non-MVV-Aware Attributes

When ((var)) is used on a widget attribute that does not support multi-valued variables (such as the text attribute of the TextWidget), only the first value is used:

<$text text=((myvar))/>

Passing Multi-Valued Variables to Procedures

The primary use case for this syntax is passing multi-valued variables through the $transclude pipeline to procedures and functions:

\procedure showItems(itemList)
<$text text={{{ [(itemList)join[-]] }}}/>
\end

<$let items={{{ [all[tiddlers]sort[]] }}}>
<$transclude $variable="showItems" itemList=((items))/>
</$let>

In this example, the complete list of tiddler titles stored in items is passed to the itemList parameter of the showItems procedure.