RE: can't export conditional variable set with 'cond'

[M]

IMO this looks like a minimalised reproducer for a problem encountered in 
practice.

If you are going to reify variables, I would propose boxes instead, which 
simply hold a single value and hence are have very straightforward semantics 
and are very close to the semantics of variables.

Parameters have more involved semantics (reading and setting depends on the 
dynamic environment, see e.g. ‘parameterize’, also see the bit about conversion 
functions or whatever they are called), which might or might not be desired, 
depending on what you are doing. (With the provided code, it is hard to tell).

Best regards,
Maxime Devos