upgrading MacPorts after updating from 10.6 to 10.9 - missing gnutar?

["René J.V. Bertin"]

I'm continuing my endeavours after a little break ...

The "source" install I'm upgrading for 10.9 had 2 perl5 variants installed:
  perl5 @5.12.4_0+perl5_12
  perl5 @5.12.4_0+perl5_16 (active)

both presumably dependencies of ports I requested, and their upgrades over the time (I'm running 10.6 with MacPorts since autumn 2010). I also have a whole slew (55) of p5.12-* ports, and a few p5.16-* ports.

It looks like having those 2 variants may be causing reinstallation issues, as I've seen many a message referring to @perl5_12 when apparently a port didn't request a specific perl5 variant, and failures on the installation of all p5.12 ports. 
(Example extract from one of the build logs:
:notice:configure --->  Configuring p5.12-error
:debug:configure Using compiler 'Xcode Clang'
:debug:configure Executing org.macports.configure (p5.12-error)
:debug:configure Environment: CPATH='/Volumes/Debian/MacPorts/include' CFLAGS='-Os' CPPFLAGS='-I/Volumes/Debian/MacPorts/include' CXXFLAGS='-Os' LIBRARY_PATH='/Volumes/Debian/MacPorts/lib' MACOSX_DEPLOYMENT_TARGET='10.9' CXX='/usr/bin/clang++' CC_PRINT_OPTIONS_FILE='/Volumes/Debian/MacPorts/var/macports/build/_Volumes_Debian_MacPorts_var_macports_sources_rsync.macports.org_release_ports_perl_p5-error/p5.12-error/work/.CC_PRINT_OPTIONS' F90FLAGS='-Os' LDFLAGS='-L/Volumes/Debian/MacPorts/lib -Wl,-headerpad_max_install_names' FCFLAGS='-Os' OBJC='/usr/bin/clang' OBJCXX='/usr/bin/clang++' INSTALL='/usr/bin/install -c' PERL_AUTOINSTALL='--skipdeps' FFLAGS='-Os' OBJCFLAGS='-Os' OBJCXXFLAGS='-Os' CC_PRINT_OPTIONS='YES' CC='/usr/bin/clang'
:debug:configure Assembled command: 'cd "/Volumes/Debian/MacPorts/var/macports/build/_Volumes_Debian_MacPorts_var_macports_sources_rsync.macports.org_release_ports_perl_p5-error/p5.12-error/work/Error-0.17016" && /Volumes/Debian/MacPorts/bin/perl5.12 Makefile.PL INSTALLDIRS=vendor CC="/usr/bin/clang" LD="/usr/bin/clang"'
:debug:configure Executing command line:  cd "/Volumes/Debian/MacPorts/var/macports/build/_Volumes_Debian_MacPorts_var_macports_sources_rsync.macports.org_release_ports_perl_p5-error/p5.12-error/work/Error-0.17016" && /Volumes/Debian/MacPorts/bin/perl5.12 Makefile.PL INSTALLDIRS=vendor CC="/usr/bin/clang" LD="/usr/bin/clang" 
:info:configure Checking if your kit is complete...
:info:configure Looks good
:info:configure CPAN::Meta::YAML 0.002 is not available
:info:configure  at /Volumes/Debian/MacPorts/lib/perl5/site_perl/5.12.4/CPAN/Meta.pm line 320.
:info:configure Command failed:  cd "/Volumes/Debian/MacPorts/var/macports/build/_Volumes_Debian_MacPorts_var_macports_sources_rsync.macports.org_release_ports_perl_p5-error/p5.12-error/work/Error-0.17016" && /Volumes/Debian/MacPorts/bin/perl5.12 Makefile.PL INSTALLDIRS=vendor CC="/usr/bin/clang" LD="/usr/bin/clang" 
:info:configure Exit code: 2
:error:configure org.macports.configure for port p5.12-error returned: configure failure: command execution failed
:debug:configure Error code: NONE
:debug:configure Backtrace: configure failure: command execution failed
    while executing
"$procedure $targetname"
:info:configure Warning: targets not executed for p5.12-error: org.macports.activate org.macports.configure org.macports.build org.macports.destroot org.macports.install
:error:configure Failed to install p5.12-error
:debug:configure Registry error: p5.12-net-ssleay not registered as installed & active.
    invoked from within
"registry_active ${subport}"
    invoked from within
"$workername eval registry_active \${subport}"
:notice:configure Please see the log file for port p5.12-error for details:
    /Volumes/Debian/MacPorts/var/macports/logs/_Volumes_Debian_MacPorts_var_macports_sources_rsync.macports.org_release_ports_perl_p5-error/p5.12-error/main.log
)

I hope I haven't overlooked anything in the docs, but how does the restore.tcl script handle multiple perl5 variants/versions? Given that I do not myself have any direct requirements on perl versions, shouldn't I just have removed all references to specific perl5 versions/variants, or bumped all +perl5_12 to +perl5_16? If so, can I rectify that WITHOUT having to start everything from scratch?