C:\test>perl -aF, -nle"}{print $_,' ', $i++ for @F" junk.txt
SUBNET_ID 0
AUTONOMOUS_NETWORK_ID 1
PARENT_ID 2
TREE_PATH 3
SUBNET 4
CIDR_MASK 5
IP_VERSION 6
LOW_ADDRESS 7
HIGH_ADDRESS 8
BROADCAST_ADDRESS 9
SHORT_SUBNET 10
ASSIGNED_ADDRESSES 11
CHILD_SUBNET_COUNT 12
COMMENT 13
SYSTEM_FLAG1 14
REPLICATED_FROM 15
CREATED 16
UPDATED 17
LOCATION 18
USAGE 19
NETWORK_NAME 20