Sigh.  The regexec matcher in libc 5.4.44 = GNU regex-0.12 loops on this:

-  regexec (regcomp "\\(\\*([^\\*]*(\\*|[^\\)])?)*\\*\\)" [Extended]) [] "(*hjdshf  * *)sds(*bad *)    \n\touue ";

The problem appears in a C program, too:

/* Try GNU implementation of POSIX regex */

#include <stdlib.h>
#include <sys/types.h>
#include <regex.h>

/* ML type: string -> word -> regex */

void main(int argc, char* argv[]) {
  regex_t patbuf;
  char* pat = "\\(\\*([^\\*]*(\\*|[^\\)])?)*\\*\\)";
  int comperror = regcomp(&patbuf, pat, REG_EXTENDED);
  int nmatch = 1;
  regmatch_t* pmatch = (regmatch_t*)(malloc(nmatch * sizeof(regmatch_t)));
  char* str = "(*hjdshf  * *)sds(*bad *)    \n\touue ";
  int matcherror = regexec(&patbuf, str, nmatch, pmatch, 0);
  printf("%d\n", matcherror);
}

The problem does not appear if REG_NOSUB is specified.

If we remove the alternation symbol (|), which shouldn't be there
anyway, the problem goes away:

  char* pat = "\\(\\*([^\\*]*(\\*[^\\)])?)*\\*\\)";


   Define fapp f (x, r) = f x :: r
   Then 

   map regex f s = List.rev (fold regex (#2, fapp f) [] s)

   app regex f s = fold regex (fn _ => (), f o #1) () s

   fields regex f s = fold regex (fapp Substring.string, #2) [] s

   tokens regex f s = List.filter (fn s => s <> "") (fields regex f s)

   substitute regex f s = Substring.concat(fold regex (op ::, 
   fn (v, r) => f(Substring.string(Vector.sub(v, 0))) :: r) [] s)