how to change regexp captured group conditionally

[tagp...@gmail.com]

Hello,
I have a regular experission and it works perfectly.
https://regex101.com/r/wFuL72/5
In this regexp I have a "sevierity" group. it's value should be one of I,E,W,F,....
I would like to map this values in following way:

STATES = {
  "I"  => "INFO",
  "E" => "ERROR",
  "W"  => "WARNING",
  "D" => "DEBUG",
  "T"  => "TRACE",
  "F" => "FATAL"
}

and replace the maped value with regex captured single character one.

Plaes guide me.