setvar
Specifies a variable allow you to create dynamic decks and cards based on user input. Variable names are case-sensitive and consist of a ASCII letter or underscore followed by a zero or more letters, digits, or underscores. The following table describes how you can substitute variable values.
$var or $(var) Escapes the variable using URL escaping conventions in the appropriate context.
$(var:e) or $(var:escape) Escaping no alphanumeric characters according to URL encoding conventions.
$(var:unesc) Unescaping no alphanumeric characters according to URL encoding conventions.
$(var:n) or $(var:noesc) Substitutes the value of var, without escaping non-alphanumeric characters.

attributes

name
Specifies the variable name.
value
Specifies the variable value.
xml:lang
Specifies the natural or formal language in which the document is written.
id
Provides an element with a unique name within a single deck.
class
Affiliates an element with one or more classes.