diff --git a/lib/CPAN.pm b/lib/CPAN.pm
index 2d87f47f8..70fd77f21 100644
--- a/lib/CPAN.pm
+++ b/lib/CPAN.pm
@@ -2,7 +2,7 @@
 # vim: ts=4 sts=4 sw=4:
 use strict;
 package CPAN;
-$CPAN::VERSION = '2.27';
+$CPAN::VERSION = '2.27_01'; # with cperl support
 $CPAN::VERSION =~ s/_//;
 
 # we need to run chdir all over and we would get at wrong libraries
@@ -63,6 +63,7 @@ use Text::Wrap ();
 sub find_perl ();
 sub anycwd ();
 sub _uniq;
+my $CPERL = $Config::Config{usecperl};
 
 no lib ".";
 
@@ -207,6 +208,8 @@ sub soft_chdir_with_alternatives ($);
         }
         $autoload_recursion--;
     }
+    # make sure we can install any modules from CPAN without patching them
+    $ENV{PERL_USE_UNSAFE_INC} = 1;
 }
 
 {
@@ -522,9 +525,10 @@ sub _flock {
 }
 
 sub _yaml_module () {
-    my $yaml_module = $CPAN::Config->{yaml_module} || "YAML";
+    my $dflt = $CPERL ? "YAML::XS" : "YAML";
+    my $yaml_module = $CPAN::Config->{yaml_module} || $dflt;
     if (
-        $yaml_module ne "YAML"
+        $yaml_module ne $dflt
         &&
         !$CPAN::META->has_inst($yaml_module)
        ) {
@@ -559,9 +563,19 @@ sub _yaml_loadfile {
         # so we do it manually instead
         my $old_loadcode = ${"$yaml_module\::LoadCode"};
         ${ "$yaml_module\::LoadCode" } = $CPAN::Config->{yaml_load_code} || 0;
+        # CPAN yaml is not strict YAML. Only Ingy YAML is strict, esp. YAML::XS
+        my $old_nonstrict = ${"$yaml_module\::NonStrict"};
+        ${ "$yaml_module\::NonStrict" } = 1 if $yaml_module =~ /^YAML(::XS)?$/;
 
         my ($code, @yaml);
-        if ($code = UNIVERSAL::can($yaml_module, "LoadFile")) {
+        if ($code = UNIVERSAL::can($yaml_module, "SafeLoadFile")) {
+            # TODO: allow CPAN::* classes
+            eval { @yaml = $code->($local_file); };
+            if ($@) {
+                # this shall not be done by the frontend
+                die CPAN::Exception::yaml_process_error->new($yaml_module,$local_file,"parse",$@);
+            }
+        } elsif ($code = UNIVERSAL::can($yaml_module, "LoadFile")) {
             eval { @yaml = $code->($local_file); };
             if ($@) {
                 # this shall not be done by the frontend
@@ -582,6 +596,11 @@ sub _yaml_loadfile {
             }
         }
         ${"$yaml_module\::LoadCode"} = $old_loadcode;
+        if (!defined $old_nonstrict) {
+            undef ${"$yaml_module\::NonStrict"};
+        } else {
+            ${"$yaml_module\::NonStrict"} = $old_nonstrict;
+        }
         return \@yaml;
     } else {
         # this shall not be done by the frontend
@@ -599,6 +618,8 @@ sub _yaml_dumpfile {
         if (UNIVERSAL::isa($local_file, "FileHandle")) {
             $code = UNIVERSAL::can($yaml_module, "Dump");
             eval { print $local_file $code->(@what) };
+        } elsif ($code = UNIVERSAL::can($yaml_module, "SafeDumpFile")) {
+            eval { $code->($local_file,@what); };
         } elsif ($code = UNIVERSAL::can($yaml_module, "DumpFile")) {
             eval { $code->($local_file,@what); };
         } elsif ($code = UNIVERSAL::can($yaml_module, "Dump")) {
diff --git a/lib/CPAN/Distribution.pm b/lib/CPAN/Distribution.pm
index 341210853..d247f185d 100644
--- a/lib/CPAN/Distribution.pm
+++ b/lib/CPAN/Distribution.pm
@@ -9,10 +9,9 @@ use File::Path ();
 use POSIX ":sys_wait_h"; 
 @CPAN::Distribution::ISA = qw(CPAN::InfoObj);
 use vars qw($VERSION);
-$VERSION = "2.27";
+$VERSION = "2.27_02"; # with cperl support
 
 my $run_allow_installing_within_test = 1; # boolean; either in test or in install, there is no third option
-
 # no prepare, because prepare is not a command on the shell command line
 # TODO: clear instance cache on reload
 my %instance;
@@ -613,8 +612,9 @@ See also http://rt.cpan.org/Ticket/Display.html?id=38932\n");
         }
     }
     $self->{build_dir} = $packagedir;
-    $self->safe_chdir($builddir);
-    File::Path::rmtree("tmp-$$");
+    $self->safe_chdir(Cwd::abs_path($builddir));
+    $self->debug("rmtree $builddir/tmp-$$") if $CPAN::DEBUG;
+    File::Path::rmtree(File::Spec->catfile(Cwd::abs_path($builddir),"tmp-$$"));
 
     $self->safe_chdir($packagedir);
     $self->_signature_business();
@@ -1336,6 +1336,7 @@ Could not determine which directory to use for looking at $dist.
         # local $ENV{PERL_USE_UNSAFE_INC} = exists $ENV{PERL_USE_UNSAFE_INC} ? $ENV{PERL_USE_UNSAFE_INC} : 1; # look
         $CPAN::META->set_perl5lib;
         local $ENV{MAKEFLAGS}; # protect us from outer make calls
+        local $ENV{PERL_USE_UNSAFE_INC} = 1;
 
         unless (system($shell) == 0) {
             my $code = $? >> 8;
@@ -2704,6 +2705,12 @@ sub follow_prereqs {
     my(@good_prereq_tuples);
     for my $p (@prereq_tuples) {
         # e.g. $p = ['Devel::PartialDump', 'r', 1]
+        # skip builtins without .pm
+        if ($Config::Config{usecperl}
+            and $p->[0] =~ /^(DynaLoader|XSLoader|strict|coretypes)$/) {
+            CPAN->debug("$p->[0] builtin") if $CPAN::DEBUG;
+            next;
+        }
         # promote if possible
         if ($p->[1] =~ /^(r|c)$/) {
             push @good_prereq_tuples, $p;
@@ -2718,6 +2725,7 @@ sub follow_prereqs {
             die "Panic: in follow_prereqs: reqtype[$p->[1]] seen, should never happen";
         }
     }
+    return unless @good_prereq_tuples;
     my $pretty_id = $self->pretty_id;
     my %map = (
                b => "build_requires",
@@ -2938,6 +2946,11 @@ sub unsat_prereq {
     my @merged = sort $merged->required_modules;
     CPAN->debug("all merged_prereqs[@merged]") if $CPAN::DEBUG;
   NEED: for my $need_module ( @merged ) {
+        # skip builtins without .pm
+        if ($^V =~ /c$/ and $need_module =~ /^(DynaLoader|XSLoader|strict|coretypes)$/) {
+            CPAN->debug("$need_module builtin") if $CPAN::DEBUG;
+            next NEED;
+        }
         my $need_version = $merged->requirements_for_module($need_module);
         my($available_version,$inst_file,$available_file,$nmo);
         if ($need_module eq "perl") {
@@ -3838,7 +3851,7 @@ sub test {
 }
 
 sub _make_test_illuminate_prereqs {
-    my($self) = @_;
+    my ($self) = @_;
     my @prereq;
 
     # local $CPAN::DEBUG = 16; # Distribution
@@ -3864,6 +3877,10 @@ sub _make_test_illuminate_prereqs {
                 ) {
             # lex Class::Accessor::Chained::Fast which has no $VERSION
             CPAN->debug("m[$m] have available_file[$available_file]")
+              if $CPAN::DEBUG;
+        } elsif ($Config::Config{usecperl}
+                 and $m =~ /^(DynaLoader|XSLoader|strict|coretypes)$/) {
+            CPAN->debug("m[$m] builtin available_version[$available_version]")
                 if $CPAN::DEBUG;
         } else {
             push @prereq, $m
diff --git a/lib/CPAN/FirstTime.pm b/lib/CPAN/FirstTime.pm
index af4a6d775..dd8f6d72e 100644
--- a/lib/CPAN/FirstTime.pm
+++ b/lib/CPAN/FirstTime.pm
@@ -11,7 +11,7 @@ use File::Spec ();
 use CPAN::Mirrors ();
 use CPAN::Version ();
 use vars qw($VERSION $auto_config);
-$VERSION = "5.5314";
+$VERSION = "5.5314_01";
 
 =head1 NAME
 
@@ -661,6 +661,9 @@ may be more alternative YAML conforming modules. When I tried two
 other players, YAML::Tiny and YAML::Perl, they seemed not powerful
 enough to work with CPAN.pm. This may have changed in the meantime.
 
+The core module CPAN::Meta::YAML cannot load YAML 1.2 !! features,
+used for C<!!perl/hash:CPAN::Distribution> hashes.
+
 Which YAML implementation would you prefer?
 
 =back
@@ -814,6 +817,39 @@ then restart your command line shell and CPAN before installing modules:
 
 }
 
+#
+#  YAML::Syck, YAML::XS (cperl only), YAML, YAML::Tiny. CPAN::Meta::YAML not yet
+#  YAML::XS is broken upstream, CPAN::Meta::YAML cannot read spec v2.
+#
+
+sub _yaml_init {
+    my ($matcher) = @_;
+    my $CPERL = $Config::Config{usecperl};
+    my $dflt = $CPERL ? 'YAML::XS' : 'YAML';
+    while(1) {
+        my_dflt_prompt(yaml_module => $dflt, $matcher);
+        my $given = $CPAN::Config->{yaml_module};
+        my $forbidden = $CPERL ? qr/^(CPAN::Meta::YAML)$/ : qr/^(CPAN::Meta::YAML|YAML::XS)$/;
+        if ($given =~ $forbidden) {
+            $CPAN::Frontend->mywarn
+              ("Error: $given cannot be used yet. Try YAML"
+               . $CPERL ? ", YAML::Syck or YAML::XS\n" : " or YAML::Syck\n");
+            $CPAN::Frontend->mysleep(3);
+        } else {
+            last;
+        }
+    }
+    my $old_v = $CPAN::Config->{load_module_verbosity};
+    $CPAN::Config->{load_module_verbosity} = q[none];
+    if (!$auto_config && !$CPAN::META->has_inst($CPAN::Config->{yaml_module})) {
+        $CPAN::Frontend->mywarn
+          ("Warning (maybe harmless): '$CPAN::Config->{yaml_module}' not installed. Try $dflt\n");
+        $CPAN::Frontend->mysleep(3);
+    }
+    $CPAN::Config->{load_module_verbosity} = $old_v;
+}
+
+
 sub init {
     my($configpm, %args) = @_;
     use Config;
@@ -983,23 +1019,13 @@ sub init {
 
     my_yn_prompt(trust_test_report_history => 0, $matcher);
 
-    #
-    #= YAML vs. YAML::Syck
-    #
+    #= YAML module
     if (!$matcher or "yaml_module" =~ /$matcher/) {
-        my_dflt_prompt(yaml_module => "YAML", $matcher);
-        my $old_v = $CPAN::Config->{load_module_verbosity};
-        $CPAN::Config->{load_module_verbosity} = q[none];
-        if (!$auto_config && !$CPAN::META->has_inst($CPAN::Config->{yaml_module})) {
-            $CPAN::Frontend->mywarn
-                ("Warning (maybe harmless): '$CPAN::Config->{yaml_module}' not installed.\n");
-            $CPAN::Frontend->mysleep(3);
-        }
-        $CPAN::Config->{load_module_verbosity} = $old_v;
+        _yaml_init($matcher);
     }
 
     #
-    #= YAML code deserialisation
+    #= YAML code deserialisation (security problem)
     #
     my_yn_prompt(yaml_load_code => 0, $matcher);
 
@@ -2181,6 +2207,4 @@ sub prompt_no_strip ($;$) {
     return _real_prompt(@_);
 }
 
-
-
 1;
diff --git a/lib/CPAN/Version.pm b/lib/CPAN/Version.pm
index fa75221d9..5acc19c99 100644
--- a/lib/CPAN/Version.pm
+++ b/lib/CPAN/Version.pm
@@ -2,7 +2,7 @@ package CPAN::Version;
 
 use strict;
 use vars qw($VERSION);
-$VERSION = "5.5003";
+$VERSION = "5.5003_01"; # with cperl support
 
 # CPAN::Version::vcmp courtesy Jost Krieger
 sub vcmp {
@@ -18,6 +18,7 @@ sub vcmp {
 
     for ($l,$r) {
         s/_//g;
+        s/c$//;
     }
     CPAN->debug("l[$l] r[$r]") if $CPAN::DEBUG;
     for ($l,$r) {
diff --git a/t/04clean_load.t b/t/04clean_load.t
index 18a4e6e46..21bdd266f 100644
--- a/t/04clean_load.t
+++ b/t/04clean_load.t
@@ -11,7 +11,7 @@ my %has_deps = (
 
 my @modules;
 use File::Find;
-find(\&list_modules, 'blib/lib');
+find(\&list_modules, $ENV{PERL_CORE} ? 'lib' : 'blib/lib');
 
 use Test::More;
 plan(tests => scalar @modules);
diff --git a/t/31sessions.t b/t/31sessions.t
index 9ef32cb77..baedeb8ee 100644
--- a/t/31sessions.t
+++ b/t/31sessions.t
@@ -358,6 +358,7 @@ EOF
            "make CPAN::Test::Dummy::Perl5::Build::Fails" => "Has.already.been.unwrapped",
            "test CPAN::Test::Dummy::Perl5::Build::Fails" => "(?i:t/00_load.+FAILED)",
            "o conf dontload_list push YAML" => ".",
+           "o conf dontload_list push YAML::XS" => ".",
            "o conf dontload_list push YAML::Syck" => ".",
            "o conf dontload_list push Parse::CPAN::Meta" => ".",
            "o conf dontload_list push CPAN::Meta" => ".",
@@ -428,6 +429,7 @@ EOF
            "o conf dontload_list pop" => ".",
            "o conf dontload_list pop" => ".",
            "o conf dontload_list pop" => ".",
+           "o conf dontload_list pop" => ".",
            "o conf commit" => "commit: wrote",
           ],
          },
diff --git a/t/41distribution.t b/t/41distribution.t
index e09929df2..f5a87b581 100644
--- a/t/41distribution.t
+++ b/t/41distribution.t
@@ -1,5 +1,5 @@
 # Test CPAN::Distribution objects
-# 
+#
 # Very, very preliminary API testing, but we have to start somewhere
 
 BEGIN {
@@ -17,7 +17,7 @@ BEGIN {
     my $yaml_module = CPAN::_yaml_module();
     my $exit_message;
     if ($CPAN::META->has_inst($yaml_module)) {
-        # print "# yaml_module[$yaml_module] loadable\n";
+        #print STDERR "# yaml_module[$yaml_module] loadable\n";
     } else {
         $exit_message = "No yaml module installed";
     }
@@ -44,8 +44,7 @@ use File::Temp qw(tempdir);
 use File::Spec::Functions qw/catdir catfile/;
 use File::Basename qw/basename/;
 
-use lib "inc";
-use lib "t";
+use lib $Config::Config{usecperl} ? ("t") : ("inc", "t");
 use local_utils;
 use version;
 
diff --git a/t/44cpanmeta.t b/t/44cpanmeta.t
index ba572a291..0c20742a2 100644
--- a/t/44cpanmeta.t
+++ b/t/44cpanmeta.t
@@ -28,8 +28,7 @@ use File::Temp qw(tempdir);
 use File::Spec::Functions qw/catdir catfile/;
 use File::Basename qw/basename/;
 
-use lib "inc";
-use lib "t";
+use lib $Config::Config{usecperl} ? ("t") : ("inc", "t");
 use local_utils;
 
 # prepare local CPAN