+#define PST_ENDALIAS 0x200000 /* just finished expanding and consuming an alias */
+#define PST_NOEXPAND 0x400000 /* don't expand anything in read_token_word; for command substitution */
+#define PST_NOERROR 0x800000 /* don't print error messages in yyerror */
+#define PST_STRING 0x1000000 /* parsing a string to a command or word list */