Dynamic keys in multi-select-hash

[innovate-invent]

I often want to be able to specify a key name dynamically when defining a multi-select-hash:
{expression1: expression2} where the result of expression1 is the key for that key-value.

The key is already spec'd as an unquoted identifier which is used literally rather than searching the current context. This collides with the ability to use an expression: search({a: "foo", bar: 5}, {a: bar}) -> {a: 5} a is used literally rather than trying to de-reference it as "foo" resulting in {foo: 5}.

This could be worked around by using parenthesis when wanting a dynamic key: {(a): bar} -> {foo: 5}. This is similar to Computed Property Names in Javascript.

This feature becomes more important when you consider its use with reduce(): search([["foo", 1], ["bar", 2]], &[%].$+{[ @[0] ]: @[1]}) -> {foo: 1, bar: 2}
This is the equivalent to the proposed from_items()

The proposed grammar change would be:

keyval-expr       = ( identifier / paren-expression ) ":" expression

Originally mentioned here