GAMS $macro

GAMS 22.9 has some macro facilities. I don't completely understand it. The following model:

$macro a b
scalar a/1/;
display a;

gives:

   1  $macro a b
   2  scalar a/1/;
****         $195,409
**** 195  Symbol redefined with a different type
**** 409  Unrecognizable item - skip to find a new statement
****        looking for a ';' or a key word to get started again
   3  display b;
****          $140
**** 140  Unknown symbol

**** 3 ERROR(S)   0 WARNING(S)

Apparently it is skipping some substitutions. This is not like what I am used to in macro preprocessors for languages like C and Delphi.

I would expect this model to behave like:

scalar b/1/;
display b;