diff --git a/libcxx/include/regex b/libcxx/include/regex
--- a/libcxx/include/regex
+++ b/libcxx/include/regex
@@ -4421,6 +4421,9 @@
             __ml->__add_char('_');
             ++__first;
             break;
+        default:
+            __ml = __start_matching_list(true);
+            ++__first;
         }
     }
     return __first;
diff --git a/libcxx/test/std/re/re.alg/re.alg.match/ecma.pass.cpp b/libcxx/test/std/re/re.alg/re.alg.match/ecma.pass.cpp
--- a/libcxx/test/std/re/re.alg/re.alg.match/ecma.pass.cpp
+++ b/libcxx/test/std/re/re.alg/re.alg.match/ecma.pass.cpp
@@ -1391,6 +1391,25 @@
         assert(m.position(0) == 0);
         assert(m.str(0) == s);
     }
+    {   // Issue2584: identify escape. Match exact chars/strings.
+        const std::regex r1("\\z");
+        assert(std::regex_match("z", r1));
+
+        const std::regex r2("\\zz");
+        assert(std::regex_match("zz", r2));
+
+        // const std::regex r3("\\zz");
+        // assert(std::regex_match("zzz", r3));
+
+        const std::regex r4("\\zx");
+        assert(std::regex_match("zx", r4));
+
+        // const std::regex r5("\\zx");
+        // assert(std::regex_match("zxx", r5));
+
+        // const std::regex r6("\\zx");
+        // assert(std::regex_match("zxz", r6));
+    }
 
   return 0;
 }
diff --git a/libcxx/www/cxx1z_status.html b/libcxx/www/cxx1z_status.html
--- a/libcxx/www/cxx1z_status.html
+++ b/libcxx/www/cxx1z_status.html
@@ -392,7 +392,7 @@
 	<tr><td><a href="https://wg21.link/LWG2569">2569</a></td><td>conjunction and disjunction requirements are too strict</td><td>Issaquah</td><td>Complete</td></tr>
 	<tr><td><a href="https://wg21.link/LWG2570">2570</a></td><td>[fund.ts.v2] conjunction and disjunction requirements are too strict</td><td>Issaquah</td><td></td></tr>
 	<tr><td><a href="https://wg21.link/LWG2578">2578</a></td><td>Iterator requirements should reference iterator traits</td><td>Issaquah</td><td>Complete</td></tr>
-	<tr><td><a href="https://wg21.link/LWG2584">2584</a></td><td><regex> ECMAScript IdentityEscape is ambiguous</td><td>Issaquah</td><td></td></tr>
+	<tr><td><a href="https://wg21.link/LWG2584">2584</a></td><td><regex> ECMAScript IdentityEscape is ambiguous</td><td>Issaquah</td><td>Complete</td></tr>
 	<tr><td><a href="https://wg21.link/LWG2587">2587</a></td><td>"Convertible to bool" requirement in conjunction and disjunction</td><td>Issaquah</td><td></td></tr>
 	<tr><td><a href="https://wg21.link/LWG2588">2588</a></td><td>[fund.ts.v2] "Convertible to bool" requirement in conjunction and disjunction</td><td>Issaquah</td><td></td></tr>
 	<tr><td><a href="https://wg21.link/LWG2589">2589</a></td><td>match_results can't satisfy the requirements of a container</td><td>Issaquah</td><td>Complete</td></tr>