Dynamic Macros and the Dependency List: Delayed Macro References

Dynamic macros are assigned while processing any and all targets. They can be used within the target rule as is, or in the dependency list by prepending an additional $ character to the reference. A reference beginning with $$ is called a delayed reference to a macro. For instance, the entry:

x.o y.o z.o: $$@.BAK 
         cp $@.BAK $@

could be used to derive x.o from x.o.BAK, and so forth for y.o and z.o.