[i]<target name="check-props">
 
	<!-- Ensure that entry doesn't exists in list -->
        <condition property="entry-exists">
             <contains string="${tag.list}" substring="${build.label}" />
        </condition>
        <fail if="entry-exists" message="Entry already exists.Please specify another." />
 
	<!-- Ensure dir is configured correctly and exists-->
        <condition property="dir-configured">
            <and>
                <isset property="dir" />
                <available file="${dir}" type="dir" />
            </and>
        </condition>
        <fail unless="dir-configured" message="dir not configured" />
 
</target>
 
<!-- Execute the ant based on condition is set or not -->
<target name="-set-props-if-set" if="property1">
	    <property name="property2" value="string1"/>
	    <property name="property3" value="string2"/>
</target>
 
<target name="-set-props-if-not-set" unless="property1">
	    <property name="property2" value="string2"/>
	    <property name="property3" value="string1"/>
</target>[/i]