FindPerlLibs: properly detect libperl on Windows (#12224)

This also cleans up a bunch of things on the way:
-when perl was queried for paths they were not converted to CMake style on
 Windows.
-the result when perl was queried for the perl library name was ignored since
 it was expanded with the possible paths, which is not a valid input for
 find_library(). If perl returns a library name we now will look only for this
 name and not for the default names and use the default names only when the
 executable does not give us a hint.
-get rid of 2 variables that were only used at one place and directly put the
 values in the call to find_library() and find_path().

Inspired by Jeff Trull

Modules/FindPerlLibs.cmake

@@ -94,6 +94,7 @@ if (PERL_EXECUTABLE)
   )
   if (NOT PERL_SITESEARCH_RESULT_VARIABLE)
     string(REGEX REPLACE "install[a-z]+='([^']+)'.*" "\\1" PERL_SITESEARCH ${PERL_SITESEARCH_OUTPUT_VARIABLE})
+    file(TO_CMAKE_PATH "${PERL_SITESEARCH}" PERL_SITESEARCH)
   endif (NOT PERL_SITESEARCH_RESULT_VARIABLE)
 
   ### PERL_SITELIB
@@ -107,6 +108,7 @@ if (PERL_EXECUTABLE)
   )
   if (NOT PERL_SITELIB_RESULT_VARIABLE)
     string(REGEX REPLACE "install[a-z]+='([^']+)'.*" "\\1" PERL_SITELIB ${PERL_SITELIB_OUTPUT_VARIABLE})
+    file(TO_CMAKE_PATH "${PERL_SITELIB}" PERL_SITELIB)
   endif (NOT PERL_SITELIB_RESULT_VARIABLE)
 
   ### PERL_VENDORARCH
@@ -120,6 +122,7 @@ if (PERL_EXECUTABLE)
     )
   if (NOT PERL_VENDORARCH_RESULT_VARIABLE)
     string(REGEX REPLACE "install[a-z]+='([^']+)'.*" "\\1" PERL_VENDORARCH ${PERL_VENDORARCH_OUTPUT_VARIABLE})
+    file(TO_CMAKE_PATH "${PERL_VENDORARCH}" PERL_VENDORARCH)
   endif (NOT PERL_VENDORARCH_RESULT_VARIABLE)
 
   ### PERL_VENDORLIB
@@ -133,6 +136,7 @@ if (PERL_EXECUTABLE)
   )
   if (NOT PERL_VENDORLIB_RESULT_VARIABLE)
     string(REGEX REPLACE "install[a-z]+='([^']+)'.*" "\\1" PERL_VENDORLIB ${PERL_VENDORLIB_OUTPUT_VARIABLE})
+    file(TO_CMAKE_PATH "${PERL_VENDORLIB}" PERL_VENDORLIB)
   endif (NOT PERL_VENDORLIB_RESULT_VARIABLE)
 
   macro(perl_adjust_darwin_lib_variable varname)
@@ -173,6 +177,7 @@ if (PERL_EXECUTABLE)
   if (NOT PERL_ARCHLIB_RESULT_VARIABLE)
     string(REGEX REPLACE "install[a-z]+='([^']+)'.*" "\\1" PERL_ARCHLIB ${PERL_ARCHLIB_OUTPUT_VARIABLE})
     perl_adjust_darwin_lib_variable( ARCHLIB )
+    file(TO_CMAKE_PATH "${PERL_ARCHLIB}" PERL_ARCHLIB)
   endif (NOT PERL_ARCHLIB_RESULT_VARIABLE)
 
   ### PERL_PRIVLIB
@@ -187,28 +192,10 @@ if (PERL_EXECUTABLE)
   if (NOT PERL_PRIVLIB_RESULT_VARIABLE)
     string(REGEX REPLACE "install[a-z]+='([^']+)'.*" "\\1" PERL_PRIVLIB ${PERL_PRIVLIB_OUTPUT_VARIABLE})
     perl_adjust_darwin_lib_variable( PRIVLIB )
+    file(TO_CMAKE_PATH "${PERL_PRIVLIB}" PERL_PRIVLIB)
   endif (NOT PERL_PRIVLIB_RESULT_VARIABLE)
 
-
+  ### PERL_POSSIBLE_LIBRARY_NAMES
-  ### PERL_POSSIBLE_INCLUDE_PATHS
-  set(PERL_POSSIBLE_INCLUDE_PATHS
-    ${PERL_ARCHLIB}/CORE
-    /usr/lib/perl5/${PERL_VERSION_STRING}/${PERL_ARCHNAME}/CORE
-    /usr/lib/perl/${PERL_VERSION_STRING}/${PERL_ARCHNAME}/CORE
-    /usr/lib/perl5/${PERL_VERSION_STRING}/CORE
-    /usr/lib/perl/${PERL_VERSION_STRING}/CORE
-    )
-
-  ### PERL_POSSIBLE_LIB_PATHS
-  set(PERL_POSSIBLE_LIB_PATHS
-    ${PERL_ARCHLIB}/CORE
-    /usr/lib/perl5/${PERL_VERSION_STRING}/${PERL_ARCHNAME}/CORE
-    /usr/lib/perl/${PERL_VERSION_STRING}/${PERL_ARCHNAME}/CORE
-    /usr/lib/perl5/${PERL_VERSION_STRING}/CORE
-    /usr/lib/perl/${PERL_VERSION_STRING}/CORE
-  )
-
-  ### PERL_POSSIBLE_LIBRARY_NAME
   execute_process(
     COMMAND
       ${PERL_EXECUTABLE} -V:libperl
@@ -218,10 +205,9 @@ if (PERL_EXECUTABLE)
       PERL_LIBRARY_RESULT_VARIABLE
   )
   if (NOT PERL_LIBRARY_RESULT_VARIABLE)
-    foreach(_perl_lib_path ${PERL_POSSIBLE_LIB_PATHS})
+    string(REGEX REPLACE "libperl='([^']+)'.*" "\\1" PERL_POSSIBLE_LIBRARY_NAMES ${PERL_LIBRARY_OUTPUT_VARIABLE})
-      string(REGEX REPLACE "libperl='([^']+)'" "\\1" PERL_LIBRARY_OUTPUT_VARIABLE ${PERL_LIBRARY_OUTPUT_VARIABLE})
+  else (NOT PERL_LIBRARY_RESULT_VARIABLE)
-      set(PERL_POSSIBLE_LIBRARY_NAME ${PERL_POSSIBLE_LIBRARY_NAME} "${_perl_lib_path}/${PERL_LIBRARY_OUTPUT_VARIABLE}")
+    set(PERL_POSSIBLE_LIBRARY_NAMES perl${PERL_VERSION_STRING} perl)
-    endforeach(_perl_lib_path ${PERL_POSSIBLE_LIB_PATHS})
   endif (NOT PERL_LIBRARY_RESULT_VARIABLE)
 
   ### PERL_INCLUDE_PATH
@@ -229,17 +215,23 @@ if (PERL_EXECUTABLE)
     NAMES
       perl.h
     PATHS
-      ${PERL_POSSIBLE_INCLUDE_PATHS}
+      ${PERL_ARCHLIB}/CORE
+      /usr/lib/perl5/${PERL_VERSION_STRING}/${PERL_ARCHNAME}/CORE
+      /usr/lib/perl/${PERL_VERSION_STRING}/${PERL_ARCHNAME}/CORE
+      /usr/lib/perl5/${PERL_VERSION_STRING}/CORE
+      /usr/lib/perl/${PERL_VERSION_STRING}/CORE
   )
-  
+
   ### PERL_LIBRARY
   find_library(PERL_LIBRARY
     NAMES
-      ${PERL_POSSIBLE_LIBRARY_NAME}
+      ${PERL_POSSIBLE_LIBRARY_NAMES}
-      perl${PERL_VERSION_STRING}
-      perl
     PATHS
-      ${PERL_POSSIBLE_LIB_PATHS}
+      ${PERL_ARCHLIB}/CORE
+      /usr/lib/perl5/${PERL_VERSION_STRING}/${PERL_ARCHNAME}/CORE
+      /usr/lib/perl/${PERL_VERSION_STRING}/${PERL_ARCHNAME}/CORE
+      /usr/lib/perl5/${PERL_VERSION_STRING}/CORE
+      /usr/lib/perl/${PERL_VERSION_STRING}/CORE
   )
 
 endif (PERL_EXECUTABLE)
@@ -254,7 +246,7 @@ find_package_handle_standard_args(PerlLibs REQUIRED_VARS PERL_LIBRARY PERL_INCLU
 set(PERL_INCLUDE_DIR  ${PERL_INCLUDE_PATH})
 set(PERL_INCLUDE_DIRS ${PERL_INCLUDE_PATH})
 set(PERL_LIBRARIES    ${PERL_LIBRARY})
-# For backward compatibility with CMake before 2.8.7
+# For backward compatibility with CMake before 2.8.8
 set(PERL_VERSION ${PERL_VERSION_STRING})
 
 mark_as_advanced(