guile-config: How do I use a <codex>?

[sirgazil]

I designed the following CLI for an example program that pretends to control 
irrigation sprinklers.

  $ sprinklers
  Display some information about the sprinklers in the farm.

  $ sprinklers start-all
  All sprinklers started.

  $ sprinklers stop-all
  All sprinklers stopped.

  $ sprinklers start A5
  Sprinkler A5 started.

  $ sprinklers stop A5
  Sprinkler A5 stopped.

All subcommands accept a --oscillate flag. For example:

  $ sprinklers start --oscillate A5
  Sprinkler A5 started in oscillation mode.

I'm trying out guile-config to declare the CLI of the program using a 
<configuration> record 
(https://gitlab.com/sirgazil/guile-lab/blob/master/scripts/cli/sprinklers#L96) 
and I have defined a "dispatcher" procedure that is supposed to run some Guile 
procedure depending on the command entered by the user 
(https://gitlab.com/sirgazil/guile-lab/blob/master/scripts/cli/sprinklers#L165).
 But I don't understand how to use the <codex> record for that purpose (I'm 
currently matching command patterns against the result of (command-line) 
instead to make the example program work).

So, for example, using the <codex> record, how would I map the following command

  $ sprinklers start A5

to a Guile procedure like

  (define (sprinkler-start id) ...)


Thanks,

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