+${CHANNEL} Current channel name
+${ENV(VAR)} Environmental variable VAR
+${LEN(VAR)} String length of VAR (integer)
+${EPOCH} Current unix style epoch
+${DATETIME} Current date time in the format: YYYY-MM-DD_HH:MM:SS
+${UNIQUEID} Current call unique identifier
+${DNID} Dialed Number Identifier
+${RDNIS} Redirected Dial Number ID Service
+${HANGUPCAUSE} Hangup cause on last PRI hangup
+${SIPDOMAIN} SIP destination domain of an inbound call (if appropriate)