Thanks for all your suggestions ...
I could not get, $set assign-printer($Linux.Environment.Variable), to work.
But I did get , ASSIGN TO PRINTER"$Linux.Environment.Variable", to work.
I'm probably going to use the "ASSIGN TO PRINTER" method, just because I know we have reports that print multiple documents to multiple printers, and that will give me that degree of control.
I'm not sure what I did wrong with the compiler directive method, hopefully this thinking won't come back to haunt me later.