ENH: find perl with FindPerl not find_program, bug: 6243

Modules/FindPerlLibs.cmake

@@ -22,8 +22,9 @@ SET(PERL_POSSIBLE_LIB_PATHS
 FIND_PATH(PERL_INCLUDE_PATH perl.h
   ${PERL_POSSIBLE_INCLUDE_PATHS})
 
+# find the perl executable
+INCLUDE(FindPerl)
 
-FIND_PROGRAM(PERL_EXECUTABLE perl )
 
 IF(PERL_EXECUTABLE)
   EXEC_PROGRAM(${PERL_EXECUTABLE}