define condition

define condition <name>: <condition> names a condition so you can reuse it by name. The name is a single hyphenated token (not a multi-word prose name), and the body is the ordinary condition grammar.

define condition trug-in-hand: the player holds the trug
define condition ripe-tomato: it is a tomato and it is not in the trug

The distinction that matters is open versus closed, and it is decided entirely by whether the body mentions it:

• A closed condition never mentions it. It is a plain truth test about the world: trug-in-hand asks whether the player holds the trug, yes or no. Closed conditions go in truth positions: while, when, refuse when, must be comparisons.
• An open condition mentions it, leaving the subject free. It describes a set: ripe-tomato is the criterion "any tomato not yet in the trug." Open conditions go where a set is expected: any/no/each and must be any.

  on examining it
    phrase go-ahead when trug-in-hand
    phrase still-out when any ripe-tomato
  end on

Using one where the other belongs is a load error, never a silent guess: any over a closed condition is analysis.closed-condition-selection, and a bare open condition in a truth position is analysis.open-condition-truth. The rule of thumb is "mention it when you mean a set, leave it out when you mean a fact."