Perhaps this is common knowledge (still not documented anywhere, though, and I'd say the official documentation is downright confusing regarding this), but dollar sign expansions of this type:

$(=Expression)

work in object formulas, but don't work in the load script. In script, they always evaluate to null/empty string.

There is one exception though - if the expression is a single number literal, it will work. So this:

$(=123)

will still evaluate to the number 123, no matter if used in script or in the frontend.

This can be occasionally useful if you have defined a variable which takes other variables' names as parameters, which are then called with $($1) syntax. If you replace one of the parameters with e.g. =123, you can pass a numeric constant as a parameter instead of having to use a variable.