Parse JSON value into separate strings in telegraf.conf

Question

I am using telegraf inputs.tail to parse my application log files. Input data is in json format like so:

{
"key1":"value1",
"key2":"value2",
"key3":"value3a^value3b"
}

Question - How to parse the value of key3 so that I can write value3a and value3b to two separate tags/columns in influxDB?

telegraf.conf snippet:

[[inputs.tail]]

files = ["/path/to/log/server.log"]

data_format = "json"

  tag_keys = [
    "key1",
    "key2",
    "key3"
  ]

Been breaking my head with this problem for 2 days now. Any help would be much appreciated! Thanks in advance.