diff --git a/Modules/ExternalData.cmake b/Modules/ExternalData.cmake
index 0ef514c1f..6442c3ee9 100644
--- a/Modules/ExternalData.cmake
+++ b/Modules/ExternalData.cmake
@@ -502,11 +502,14 @@ endmacro()
 function(_ExternalData_arg_find_files pattern regex)
   file(GLOB globbed RELATIVE "${top_src}" "${top_src}/${pattern}*")
   foreach(entry IN LISTS globbed)
-    string(REGEX REPLACE "^(${regex})(\\.md5|)$" "\\1;\\2" tuple "${entry}")
-    list(LENGTH tuple len)
-    if("${len}" EQUAL 2 AND NOT IS_DIRECTORY "${top_src}/${entry}")
-      list(GET tuple 0 relname)
-      list(GET tuple 1 alg)
+    if("x${entry}" MATCHES "^x(.*)(\\.md5)$")
+      set(relname "${CMAKE_MATCH_1}")
+      set(alg "${CMAKE_MATCH_2}")
+    else()
+      set(relname "${entry}")
+      set(alg "")
+    endif()
+    if("x${relname}" MATCHES "^x${regex}$" AND NOT IS_DIRECTORY "${top_src}/${entry}")
       set(name "${top_src}/${relname}")
       set(file "${top_bin}/${relname}")
       if(alg)
diff --git a/Tests/Module/ExternalData/Data2/CMakeLists.txt b/Tests/Module/ExternalData/Data2/CMakeLists.txt
index f8eedff64..e6d8767a6 100644
--- a/Tests/Module/ExternalData/Data2/CMakeLists.txt
+++ b/Tests/Module/ExternalData/Data2/CMakeLists.txt
@@ -1,5 +1,5 @@
 set(ExternalData_SERIES_PARSE "([0-9]+)(_\\.my\\.dat)$")
-set(ExternalData_SERIES_MATCH "[0-9]+")
+set(ExternalData_SERIES_MATCH "([0-9]+)")
 ExternalData_Add_Test(Data2
   NAME Data2Check
   COMMAND ${CMAKE_COMMAND}