-- `?h cond a b` — general prefix-ternary keyword with three
-- operand atoms. Reads as `if cond then a else b`. The literal
-- `h` is the keyword (analogous to `=`/`>`/`<` in `?=`/`?>`/`?<`)
-- and `cond` can be any bool-valued expression-as-atom: a ref,
-- a comparison-derived bool, a predicate-call result.
--
-- This complements PR #330's bool-subject `?h a b` shape (which
-- takes exactly two operand atoms — there the `h` is a bool
-- variable, not the keyword). The disambiguator is operand
-- count: two atoms after `?h` → bool-subject; three atoms → the
-- general keyword form below.
--
-- Use case: a let-RHS where the condition is a local bool you
-- already named something other than `h` — typically a
-- comparison result (`cn=eq x 0`) or a predicate call. The
-- brace shape `?cn{a}{b}` works too, but the prefix shape is
-- two characters cheaper per occurrence.
-- Comparison-derived bool as the condition.
clf x:n>t;cn=>x 0;?h cn "pos" "nonpos"
-- Predicate result as the condition.
known t:t>t;ok=has ["a" "b" "c"] t;?h ok "yes" "no"
-- The originating security-researcher use case: pick a JSON key
-- to read based on whether a tag matches a known string.
sev mn:t>t;cn=(=mn "v40");sc1=?h cn "metrics:nil" "metrics:ok";sc1
-- Coexistence: PR #330's 2-operand bool-subject form still wins
-- when only two operands follow.
pr330 h:b>n;?h 7 9
-- run: clf 5
-- out: pos
-- run: clf 0
-- out: nonpos
-- run: known b
-- out: yes
-- run: known z
-- out: no
-- run: sev v40
-- out: metrics:nil
-- run: sev v31
-- out: metrics:ok
-- run: pr330 true
-- out: 7
-- run: pr330 false
-- out: 9