Functions can't be defined inside ${ ... }

[Bart Schaefer <schaefer@xxxxxxxxxxxxxxxx>]

No patch for this yet (and it may be pretty ugly to make one) but
noting for future reference that none of

: ${ function foo { ... } }
: ${ foo() { ... } }
: ${ function { ... } }
: ${ () { ... } }

are successfully parsed, regardless of what appears in the { ... }.

On the other hand, `always` expressions, short-loops, etc., work fine
(unless they include a function definition).