diff --git a/src/org/joni/Config.java b/src/org/joni/Config.java
index c2a3be7..ac9a71b 100644
--- a/src/org/joni/Config.java
+++ b/src/org/joni/Config.java
@@ -22,54 +22,57 @@
 import java.io.PrintStream;
 
 public interface Config extends org.jcodings.Config {
-    final int CHAR_TABLE_SIZE = 256;
-    final boolean USE_NO_INVALID_QUANTIFIER = true;
-    final int SCANENV_MEMNODES_SIZE = 8;
-
-    final boolean USE_NAMED_GROUP = true;
-    final boolean USE_SUBEXP_CALL = true;
-    final boolean USE_PERL_SUBEXP_CALL = true;
-    final boolean USE_BACKREF_WITH_LEVEL = true;                            /* \k<name+n>, \k<name-n> */
-
-    final boolean USE_MONOMANIAC_CHECK_CAPTURES_IN_ENDLESS_REPEAT = true; /* /(?:()|())*\2/ */
-    final boolean USE_NEWLINE_AT_END_OF_STRING_HAS_EMPTY_LINE = true;     /* /\n$/ =~ "\n" */
-    final boolean USE_WARNING_REDUNDANT_NESTED_REPEAT_OPERATOR = true;
-
-    final boolean CASE_FOLD_IS_APPLIED_INSIDE_NEGATIVE_CCLASS = true;
-
-    final boolean USE_MATCH_RANGE_MUST_BE_INSIDE_OF_SPECIFIED_RANGE = false;
-    final boolean USE_CAPTURE_HISTORY = false;
-    final boolean USE_VARIABLE_META_CHARS = true;
-    final boolean USE_WORD_BEGIN_END = true;                                /* "\<": word-begin, "\>": word-end */
-    final boolean USE_FIND_LONGEST_SEARCH_ALL_OF_RANGE = true;
-    final boolean USE_SUNDAY_QUICK_SEARCH = true;
-    final boolean USE_CEC = false;
-    final boolean USE_DYNAMIC_OPTION = false;
-    final boolean USE_BYTE_MAP = OptExactInfo.OPT_EXACT_MAXLEN <= CHAR_TABLE_SIZE;
-    final boolean USE_INT_MAP_BACKWARD = false;
-
-    final int NREGION                   = 10;
-    final int MAX_BACKREF_NUM           = 1000;
-    final int MAX_CAPTURE_GROUP_NUM     = 32767;
-    final int MAX_REPEAT_NUM            = 100000;
-    final int MAX_MULTI_BYTE_RANGES_NUM = 10000;
+    final int CHAR_TABLE_SIZE = ConfigSupport.getInt("joni.char_table_size", 256);
+    final boolean USE_NO_INVALID_QUANTIFIER = ConfigSupport.getBoolean("joni.use_no_invalid_quantifier", true);
+    final int SCANENV_MEMNODES_SIZE = ConfigSupport.getInt("joni.scanenv_memnodes_size", 8);
+
+    final boolean USE_NAMED_GROUP = ConfigSupport.getBoolean("joni.use_named_group", true);
+    final boolean USE_SUBEXP_CALL = ConfigSupport.getBoolean("joni.use_subexp_call", true);
+    final boolean USE_PERL_SUBEXP_CALL = ConfigSupport.getBoolean("joni.use_perl_subexp_call", true);
+    final boolean USE_BACKREF_WITH_LEVEL = ConfigSupport.getBoolean("joni.use_backref_with_level", true); /* \k<name+n>, \k<name-n> */
+
+    final boolean USE_MONOMANIAC_CHECK_CAPTURES_IN_ENDLESS_REPEAT = ConfigSupport.getBoolean("joni.use_monomaniac_check_captures_in_endless_repeat", true); /* /(?:()|())*\2/ */
+    final boolean USE_NEWLINE_AT_END_OF_STRING_HAS_EMPTY_LINE = ConfigSupport.getBoolean("joni.use_newline_at_end_of_string_has_empty_line", true); /* /\n$/ =~ "\n" */
+    final boolean USE_WARNING_REDUNDANT_NESTED_REPEAT_OPERATOR = ConfigSupport.getBoolean("joni.use_warning_redundant_nested_repeat_operator", true);
+
+    final boolean CASE_FOLD_IS_APPLIED_INSIDE_NEGATIVE_CCLASS = ConfigSupport.getBoolean("joni.case_fold_is_applied_inside_negative_cclass", true);
+
+    final boolean USE_MATCH_RANGE_MUST_BE_INSIDE_OF_SPECIFIED_RANGE = ConfigSupport.getBoolean("joni.use_match_range_must_be_inside_of_specified_range", false);
+    final boolean USE_CAPTURE_HISTORY = ConfigSupport.getBoolean("joni.use_capture_history", false);
+    final boolean USE_VARIABLE_META_CHARS = ConfigSupport.getBoolean("joni.use_variable_meta_chars", true);
+    final boolean USE_WORD_BEGIN_END = ConfigSupport.getBoolean("joni.use_word_begin_end", true); /* "\<": word-begin, "\>": word-end */
+    final boolean USE_FIND_LONGEST_SEARCH_ALL_OF_RANGE = ConfigSupport.getBoolean("joni.use_find_longest_search_all_of_range", true);
+    final boolean USE_SUNDAY_QUICK_SEARCH = ConfigSupport.getBoolean("joni.use_sunday_quick_search", true);
+    final boolean USE_CEC = ConfigSupport.getBoolean("joni.use_cec", false);
+    final boolean USE_DYNAMIC_OPTION = ConfigSupport.getBoolean("joni.use_dynamic_option", false);
+    final boolean USE_BYTE_MAP = ConfigSupport.getBoolean("joni.use_byte_map", OptExactInfo.OPT_EXACT_MAXLEN <= CHAR_TABLE_SIZE);
+    final boolean USE_INT_MAP_BACKWARD = ConfigSupport.getBoolean("joni.use_int_map_backward", false);
+
+    final int NREGION                   = ConfigSupport.getInt("joni.nregion", 10);
+    final int MAX_BACKREF_NUM           = ConfigSupport.getInt("joni.max_backref_num", 1000);
+    final int MAX_CAPTURE_GROUP_NUM     = ConfigSupport.getInt("joni.max_capture_group_num", 32767);
+    final int MAX_REPEAT_NUM            = ConfigSupport.getInt("joni.max_multi_byte_ranges_num", 100000);
+    final int MAX_MULTI_BYTE_RANGES_NUM = ConfigSupport.getInt("joni.max_multi_byte_ranges_num", 10000);
 
     // internal config
-    final boolean USE_OP_PUSH_OR_JUMP_EXACT         = true;
-    final boolean USE_QTFR_PEEK_NEXT                = true;
+    final boolean USE_OP_PUSH_OR_JUMP_EXACT         = ConfigSupport.getBoolean("joni.use_op_push_or_jump_exact", true);
+    final boolean USE_QTFR_PEEK_NEXT                = ConfigSupport.getBoolean("joni.use_qtfr_peek_next", true);
 
-    final int INIT_MATCH_STACK_SIZE                 = 64;
+    final int INIT_MATCH_STACK_SIZE                 = ConfigSupport.getInt("joni.init_match_stack_size", 64);
 
-    final boolean DONT_OPTIMIZE                     = false;
+    final boolean OPTIMIZE                          = ConfigSupport.getBoolean("joni.optimize", true);
+    @Deprecated
+    final boolean DONT_OPTIMIZE                     = !OPTIMIZE;
 
-    final boolean USE_STRING_TEMPLATES              = true; // use embedded string templates in Regex object as byte arrays instead of compiling them into int bytecode array
+    // use embedded string templates in Regex object as byte arrays instead of compiling them into int bytecode array
+    final boolean USE_STRING_TEMPLATES              = ConfigSupport.getBoolean("joni.use_string_templates", true);
 
 
-    final int MAX_CAPTURE_HISTORY_GROUP             = 31;
+    final int MAX_CAPTURE_HISTORY_GROUP             = ConfigSupport.getInt("joni.max_capture_history_group", 31);
 
 
-    final int CHECK_STRING_THRESHOLD_LEN            = 7;
-    final int CHECK_BUFF_MAX_SIZE                   = 0x4000;
+    final int CHECK_STRING_THRESHOLD_LEN            = ConfigSupport.getInt("joni.check_string_threshold_len", 7);
+    final int CHECK_BUFF_MAX_SIZE                   = ConfigSupport.getInt("joni.check_buff_max_size", 0x4000);
 
     final PrintStream log = System.out;
     final PrintStream err = System.err;
diff --git a/src/org/joni/ConfigSupport.java b/src/org/joni/ConfigSupport.java
index 2cd089b..99e2633 100644
--- a/src/org/joni/ConfigSupport.java
+++ b/src/org/joni/ConfigSupport.java
@@ -5,4 +5,9 @@ static boolean getBoolean(String property, boolean def) {
         String value = System.getProperty(property, def ? "true" : "false");
         return !value.equals("false");
     }
+
+    static int getInt(String property, int def) {
+        String value = System.getProperty(property);
+        return value != null ? Integer.parseInt(value) : def;
+    }
 }
diff --git a/src/org/joni/Search.java b/src/org/joni/Search.java
index 3f8ca1f..5c729fd 100644
--- a/src/org/joni/Search.java
+++ b/src/org/joni/Search.java
@@ -421,10 +421,10 @@ final int search(Matcher matcher, byte[]text, int textP, int textEnd, int textRa
             int targetP = regex.exactP;
             int targetEnd = regex.exactEnd;
 
-            int end, s, tlen1;
+            int end, s;
             int tail = targetEnd - 1;
+            int tlen1 = tail - targetP;
             if (USE_SUNDAY_QUICK_SEARCH) {
-                tlen1 = tail - targetP;
                 end = textRange + tlen1;
                 s = textP + tlen1;
             } else {