Question

Suppose my script contains a variable with the value "foo". How can I create a record with the value {foo: 3} without knowing in advance that the value might be "foo"?

Answer 1

I would think that there is another approach to your problem (especially if you are using ASObjC), but you can do this by using run script, for example:

set myLabel to text returned of (display dialog "Enter record label (key):" default answer "foo")
set myRecord to run script "return {|" & myLabel & "|:3}"

myRecord --> {foo:3} (using the default answer)

Edit: I surrounded the label (key) with pipes in case a reserved term is used.