Variable name. This follows the same syntax rules as other expression entity names: It must begin with an alpha character (A-Z or a-z) or an underscore (_). The rest of the characters must be alpha, numeric (0-9) or underscores. It cannot be re or xp (reserved for regular and XPath expressions). It cannot be an expression reserved word (e.g. SYS or HTTP). It cannot be used for an existing expression object (HTTP callout, patset, dataset, stringmap, or named expression).
This is mandatory parameter.

Initialization value for this variable, to which a singleton variable or map entry will be set if it is referenced before an assignment action has assigned it a value. If the singleton variable or map entry already has been assigned a value, setting this parameter will have no effect on that variable value. Default: 0 for ulong, NULL for text