s_subst
if ((cmd->u.s = calloc(1, sizeof (struct s_subst))) ==
compile_subst(char *p, struct s_subst *s)
compile_flags(char *p, struct s_subst *s)
static char *compile_flags(char *, struct s_subst *);
static char *compile_subst(char *, struct s_subst *);
struct s_subst *s; /* Substitute command */