See #6052. This is completely different from the +* used at the top
of doors, and has almost entirely been replaced by |$. The exception is
the use of the `%made` spec, not present in `|$`. I do not see an
obvious way to change `|$` to use `%made` since this `+*` parser uses
the name of the arm in the `%made` structure, unless we change the
AST of |$.
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