<extension name="parking_slots">
   <condition field="destination_number" expression="^(slot\d+)$" break="on-false">
     <!-- Get count of callers in the specified parking slot (FIFO) -->
     <action inline="true" application="set" data="slot_count=${fifo(count $1@demo.pbx.dynamicpacket.net)}"/>
     <action inline="true" application="set" data="slot_count=${slot_count:-3:2}"/>
   </condition>
   <condition field="${slot_count}" expression="^(\:0|ne)$" break="always">
     <!-- FIFO settings for parking FIFOs -->
     <action application="unset" data="fifo_chime_list"/>
     <action application="set" data="fifo_chime_freq=0"/>
     <!-- FIFO is empty, so park the caller: -->
     <action application="fifo" data="${destination_number}@demo.pbx.dynamicpacket.net in undef local_stream://moh"/>
     <!-- FIFO has a caller, so un-park the caller: -->
     <anti-action application="fifo" data="${destination_number}@demo.pbx.dynamicpacket.net out nowait"/>
   </condition>
 </extension>