persist lookup/delete not working in TCP CLIENT_CLOSED scope ??

Hi,

I did an iRule that persists a TCP connection with universal persistence on remote IP and port number. This works so far, but when I want to delete the persistence record when the client disconnects neither the lookup nor the delete as posted below in "when CLIENT_CLOSED" have any effect. What am I doing wrong? Will it work at all what I intent?

Cheers + hoping for a little insight,

Toralf

when CLIENT_ACCEPTED {
log local0.debug "client accepted *[IP::client_addr]:[TCP::client_port]*"
persist uie "[IP::client_addr]:[TCP::client_port]" 
TCP::collect 
}
when CLIENT_DATA {
persist uie "[IP::client_addr]:[TCP::client_port]"
TCP::release
}
when CLIENT_CLOSED {
 take a note when the client diconnects
log local0.debug "connection closed - client *[IP::client_addr]:[TCP::client_port]* "
set p [persist lookup uie { "[IP::client_addr]:[TCP::client_port]" } node]
persist delete uie { "[IP::client_addr]:[TCP::client_port]" }
log local0.debug "GPRS-closed tried to depersist *[IP::client_addr]:[TCP::client_port]*, lookup for persist node yielded $p"
}