IfVar
The <IfVar> element makes operations conditional on whether a variable exists and optionally matches a given value.
Using <IfVar>  does not change the context (the current position in the document).
| Attribute | Description | 
|---|---|
| containsRegex | The variable must contain a match to this regular expression. | 
| matches | The variable must match this value exactly. | 
| matchesRegex | The variable must match this regular expression. | 
| negate | Set this attribute to trueto perform the child operations when the variable does not exist or does not match a given value. | 
| var | The name of the variable to check. | 
The following example adds a field to the document metadata when the value of a variable named "reference" matches a regular expression.
<FieldStandardization>
    <IfVar var="reference" matchesRegex="http.*">
        <AddField name="referenceUrl" value="$(reference)" />
    </IfVar>
</FieldStandardization>