+
+Dollar doubling and macro assistance
+------------------------------------
+
+&$+ Starts dollar-doubling
+&$- Stops dollar-doubling
+ Both are idempotent and local to the file or context.
+
+While dollar-doubling:
+- - - - - - - - - - -
+
+$ => $$ including $'s produced by other
+ &-expansions not mentioned here
+
+&\$ => $
+&$NN => $(NN) where N are digits
+&$( => $(
+
+