mailcow-dockerized/data/web/inc/lib/sieve/extensions/variables.xml

<?xml version='1.0' standalone='yes'?>

<extension name="variables">

	<command name="set">
		<parameter type="tag" name="modifier" regex="(lower|upper)" occurrence="optional" />
		<parameter type="tag" name="modifier" regex="(lower|upper)first" occurrence="optional" />
		<parameter type="tag" name="modifier" regex="quotewildcard" occurrence="optional" />
		<parameter type="tag" name="modifier" regex="length" occurrence="optional" />
		<parameter type="string" name="name" regex="[[:alpha:]_][[:alnum:]_]*" />
		<parameter type="string" name="value" />
	</command>

	<test name="string">
		<parameter type="matchtype" occurrence="optional" />
		<parameter type="comparator" occurrence="optional" />
		<parameter type="stringlist" name="source" />
		<parameter type="stringlist" name="key list" />
	</test>

</extension>