Rational Developer for System z
PL/I for Windows, Version 8.0, Programming Guide

Defined macros

After you have defined a macro, you can use it anywhere in your description file with the following syntax:

$(macroname)

The parentheses are not required if the macro name is only one character long. To use a dollar sign ($) without using a macro, enter two dollar signs ($$), or use the caret (^) before the dollar sign as an escape character.

When NMAKE runs, it replaces all occurrences of $(macroname) with the defined macro string. If the macro is undefined, nothing is substituted. After a macro is defined, you can cancel it only with the !UNDEF directive.

Rational Developer for System z
PL/I for Windows, Version 8.0, Programming Guide