sub-shells handled inconsistently inside object builders

[lmorg]

Describe the bug:
An object of a variable inside an object would return a nested object. eg

murex » bob = %{a:1, b:2, c:3}
murex » %{hello: $bob}
{
    "hello": {
        "a": 1,
        "b": 2,
        "c": 3
    }
}

However a sub-shell inside an object always returns a string.

murex » function bob { %{a:1, b:2, c:3}}
murex » %{hello: ${bob}}
{
    "hello": "{\"a\":1,\"b\":2,\"c\":3}"
}

Despite that sub-shell returning a structured data type:

murex » bob -> debug -> [Data-Type]
{
    "Go": "map[string]interface {}",
    "Murex": "json",
    "UnmarshalData Err": "\u003cnil\u003e"
}

As an aside, C-style functions are also not handled consistently:

murex » %{hello: bob())}
{
    "hello": "bob())"
}

but that can be treated as a separate feature request.

Expected behaviour:

${} should be parsed as parsed as an object like variables are.

Platform (please complete the following information):

• OS, output from uname -a if supported: macOS
• Terminal Emulator: iTerm2
• Murex version, output from version --no-app-name: latest

Additional context
N/A