The annotation ensures that an error will only be thrown if the condition yields true. Without the annotation, the error will always be raised, because the referenced document is not found.
=Functions=
==Regular expressions==
{{Mark|Introduced with Version 9.1:}}
In analogy with Saxon, you can specify the flag {{Code|j}} to revert to Java’s default regex parser. For example, this allows you to use the word boundary option {{Code\b}}, which has not been included in the XQuery grammar for regular expressions:
'''Example:'''
<pre class="brush:xquery">
(: yields !abc! !def! :)
fn:replace('abc def', '\b', '!', 'j')
</pre>
=Serialization=
Various other extensions are described in the articles on [[Full-Text#BaseX Features|XQuery Full Text]] and [[Updates|XQuery Update]].
=Changelog=
# Version 9.1:
* Added: [[#Regular expressions]], {{Code|j}} flag for using Java’s default regex parser.