<configuration debug="true">

  <appender name="SIFT" class="ch.qos.logback.classic.sift.SiftingAppender">
    <discriminator>
      <key>propertyDefinedWithinSift</key>
      <defaultValue>default</defaultValue>
    </discriminator>
    <sift>
      <property name="X" value="Y"/>  

      <appender name="LIST-${propertyDefinedWithinSift}"
        class="ch.qos.logback.core.testUtil.StringListAppender">
        <layout>
          <pattern>${X}%msg</pattern>                       
        </layout>
      </appender>
    </sift>
  </appender>

  <root level="DEBUG">
    <appender-ref ref="SIFT" />
  </root>

</configuration>
