+PERL_CALLCONV void PerlIO_define_layer(pTHX_ PerlIO_funcs *tab);
+PERL_CALLCONV PerlIO_funcs *PerlIO_find_layer(pTHX_ const char *name,
+ STRLEN len,
+ int load);
+PERL_CALLCONV PerlIO *PerlIO_push(pTHX_ PerlIO *f, PERLIO_FUNCS_DECL(*tab),
+ const char *mode, SV *arg);
+PERL_CALLCONV void PerlIO_pop(pTHX_ PerlIO *f);
+PERL_CALLCONV AV* PerlIO_get_layers(pTHX_ PerlIO *f);
+PERL_CALLCONV void PerlIO_clone(pTHX_ PerlInterpreter *proto,
+ CLONE_PARAMS *param);