#define PERLIO_F_FASTGETS 0x00400000
#define PERLIO_F_TTY 0x00800000
#define PERLIO_F_NOTREG 0x01000000
+#define PERLIO_F_CLEARED 0x02000000 /* layer cleared but not freed */
#define PerlIOBase(f) (*(f))
#define PerlIOSelf(f,type) ((type *)PerlIOBase(f))