--- ./src/search.c.old	2010-02-12 14:29:01.000000000 +0100

+++ ./src/search.c	2010-02-12 14:29:18.207410166 +0100

@@ -278,6 +278,8 @@

   char eol = eolbyte;

   int backref, start, len, best_len;

   struct kwsmatch kwsm;

+  static int use_dfa;

+  static int use_dfa_checked = 0;

   size_t i, ret_val;

 #ifdef MBS_SUPPORT

   int mb_cur_max = MB_CUR_MAX;

@@ -285,6 +287,26 @@

   memset (&mbs, '\0', sizeof (mbstate_t));

 #endif /* MBS_SUPPORT */

+  if (!use_dfa_checked)

+    {

+      char *grep_use_dfa = getenv ("GREP_USE_DFA");

+      if (!grep_use_dfa)

+	{

+#ifdef MBS_SUPPORT

+	  /* Turn off DFA when processing multibyte input. */

+	  use_dfa = (MB_CUR_MAX == 1);

+#else

+	  use_dfa = 1;

+#endif /* MBS_SUPPORT */

+	}

+      else

+	{

+	  use_dfa = atoi (grep_use_dfa);

+	}

+

+      use_dfa_checked = 1;

+    }

+

   buflim = buf + size;

   for (beg = end = buf; end < buflim; beg = end)

@@ -353,7 +375,8 @@

 #endif /* MBS_SUPPORT */

 		  (kwsm.index < kwset_exact_matches))

 		goto success;

-	      if (dfaexec (&dfa, beg, end - beg, &backref) == (size_t) -1)

+	      if (use_dfa &&

+		  dfaexec (&dfa, beg, end - beg, &backref) == (size_t) -1)

 		continue;

 	    }

 	  else

@@ -362,7 +385,9 @@

 #ifdef MBS_SUPPORT

 	      size_t bytes_left = 0;

 #endif /* MBS_SUPPORT */

-	      size_t offset = dfaexec (&dfa, beg, buflim - beg, &backref);

+	      size_t offset = 0;

+	      if (use_dfa)

+		offset = dfaexec (&dfa, beg, buflim - beg, &backref);

 	      if (offset == (size_t) -1)

 		break;

 	      /* Narrow down to the line we've found. */

@@ -404,7 +429,7 @@

 		--beg;

 	    }

 	  /* Successful, no backreferences encountered! */

-	  if (!backref)

+	  if (use_dfa && !backref)

 	    goto success;

 	}

       else