How to "#ifdef" in grammer file ?

I am using a very old version of PCCTS v1.31. I want to add
conditionalized "ifdef" into grammer file like following:

actionExpr > [ CPtr<Expr> expr]:
   << CPtr<Expr> locExpr; >>
   ( deleteExpr > [$expr]
   | tryBlock > [$expr]
#ifdef LP
   | lpActionExpr > [$expr]
#endif
   ) << if (!$expr->isLVAL()) $expr = new ExprAction($expr); >>
   ;

#ifdef LP
lpActionExpr > [ CPtr<Expr> expr]:
...
#endif

I found that "#ifdef" is only allowed in "<<...>>" instead of syntax
definition level. I wonder if there is such a thing in PCCTS v1.31.

Any input is appreciated. Thanks.