--- ax_perl_ext.m4.orig	2014-02-13 10:50:08.000000000 +0100
+++ ax_perl_ext.m4	2014-02-13 10:56:56.000000000 +0100
@@ -9,11 +9,12 @@
 # DESCRIPTION
 #
 #   Fetches the linker flags and C compiler flags for compiling and linking
-#   Perl binary extensions.  The macro substitutes PERL_EXT_INC,
+#   Perl binary extensions.  The macro substitutes PERL_EXT_PREFIX, PERL_EXT_INC,
 #   PERL_EXT_LIB, PERL_EXT_CPPFLAGS, PERL_EXT_LDFLAGS and PERL_EXT_DLEXT
 #   variables if Perl executable was found.  It also checks the same
 #   variables before trying to retrieve them from the Perl configuration.
 #
+#     PERL_EXT_PREFIX: top-level perl installation path (--prefix)
 #     PERL_EXT_INC: XS include directory
 #     PERL_EXT_LIB: Perl extensions destination directory
 #     PERL_EXT_CPPFLAGS: C preprocessor flags to compile extensions
@@ -30,17 +31,16 @@
 # LICENSE
 #
 #   Copyright (c) 2011 Stanislav Sedov <address@hidden>
+#   Copyright (c) 2014 Thomas Klausner <address@hidden>
 #
 #   Redistribution and use in source and binary forms, with or without
 #   modification, are permitted provided that the following conditions are
 #   met:
 #
 #   1. Redistributions of source code must retain the above copyright
-#
 #      notice, this list of conditions and the following disclaimer.
 #
 #   2. Redistributions in binary form must reproduce the above copyright
-#
 #      notice, this list of conditions and the following disclaimer in the
 #      documentation and/or other materials provided with the distribution.
 #
@@ -68,6 +68,17 @@
         if test -n "$PERL" ; then
 
                 #
+                # Check for Perl prefix.
+                #
+                AC_ARG_VAR(PERL_EXT_PREFIX, [Perl PREFIX])
+                AC_MSG_CHECKING([for Perl prefix])
+                if test -z "$PERL_EXT_PREFIX" ; then
+                        [PERL_EXT_PREFIX=`$PERL -MConfig -e 'print $Config{prefix};'`];
+                fi
+                AC_MSG_RESULT([$PERL_EXT_PREFIX])
+                AC_SUBST(PERL_EXT_PREFIX)
+
+                #
                 # Check for Perl extensions include path.
                 #
                 AC_ARG_VAR(PERL_EXT_INC, [Directory to include XS headers from])