Dollar signs in identifiers

While non-standard, this is supported by many compilers:
http://gcc.gnu.org/onlinedocs/gcc/Dollar-Signs.html
http://llvm.org/releases/1.4/docs/ReleaseNotes.html ("Dollar sign is allowed in identifiers")
http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0348c/Ciajabbe.html