Custom calculation metrics for all values in specific labels

[melanxolik]

I found example for grafana cloud agent:

  # This stage will only run if the scraped target has a label "app"
  # with a value of "some-app" and the log line doesn't contain the word "info"
  - match:
      selector: '{app="some-app"} != "info"'
      stages:
      # The regex stage tries to extract a Go panic by looking for panic:
      # in the log message.
      - regex:
          expression: ".*(?P<panic>panic: .*)"

      # The metrics stage is going to increment a panic_total metric counter
      # which Promtail exposes. The counter is only incremented when panic
      # was extracted from the regex stage.
      - metrics:
          panic_total:
            type: Counter
            description: "total count of panic"
            source: panic
            config:
              action: inc

In my case I have a web servers which generated ton of logs and I would like to have custom metric to calculate each specific field in log record, like GET/POST/UPLOAD and etc. by separate metric value.
Is it possible?

Or I need to create a new match for each filed which I would like to calculate?