--- mod_proxy_html.c-2.4.25	2017-12-16 22:16:30.807055350 +0000
+++ mod_proxy_html.c-patched	2017-12-16 22:15:40.515448218 +0000
@@ -717,20 +717,20 @@
     const char *var;
     for (;;) {
         start = str;
-        if (start = ap_strstr_c(start, "${"), start == NULL)
+        if (start = ap_strstr_c(start, "%{ENV:"), start == NULL)
             break;
 
-        if (end = ap_strchr_c(start+2, '}'), end == NULL)
+        if (end = ap_strchr_c(start+6, '}'), end == NULL)
             break;
 
         delim = ap_strchr_c(start, '|');
         before = apr_pstrndup(r->pool, str, start-str);
         after = end+1;
         if (delim) {
-            var = apr_pstrndup(r->pool, start+2, delim-start-2);
+            var = apr_pstrndup(r->pool, start+6, delim-start-6);
         }
         else {
-            var = apr_pstrndup(r->pool, start+2, end-start-2);
+            var = apr_pstrndup(r->pool, start+6, end-start-6);
         }
         replacement = apr_table_get(r->subprocess_env, var);
         if (!replacement) {