What is Lion's version of Perl 5? What version of Perl 5 is OS X Lion shipping with?
5.12.3 - exactly:

Vigor14:~ clt$ uname -a
Darwin Vigor14 11.0.0 Darwin Kernel Version 11.0.0: Sat Jun 18 12:56:35 PDT 2011; root:xnu-1699.22.73~1/RELEASE_X86_64 x86_64
Vigor14:~ clt$ 

Vigor14:~ clt$ /usr/bin/perl -V
Summary of my perl5 (revision 5 version 12 subversion 3) configuration:

  Platform:
    osname=darwin, osvers=11.0, archname=darwin-thread-multi-2level
    uname='darwin fifth.apple.com 11.0 darwin kernel version 11.0.0: sun may 29 13:02:55 pdt 2011; root:xnu-1699.22.44~4release_x86_64 x86_64 '
    config_args='-ds -e -Dprefix=/usr -Dccflags=-g  -pipe  -Dldflags= -Dman3ext=3pm -Duseithreads -Duseshrplib -Dinc_version_list=none -Dcc=llvm-gcc-4.2'
    hint=recommended, useposix=true, d_sigaction=define
    useithreads=define, usemultiplicity=define
    useperlio=define, d_sfio=undef, uselargefiles=define, usesocks=undef
    use64bitint=define, use64bitall=define, uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
  Compiler:
    cc='llvm-gcc-4.2', ccflags ='-arch x86_64 -arch i386 -g -pipe -fno-common -DPERL_DARWIN -fno-strict-aliasing -fstack-protector -I/usr/local/include',
    optimize='-Os',
    cppflags='-g -pipe -fno-common -DPERL_DARWIN -fno-strict-aliasing -fstack-protector -I/usr/local/include'
    ccversion='', gccversion='4.2.1 (Based on Apple Inc. build 5658) (LLVM build 2335.15.00)', gccosandvers=''
    intsize=4, longsize=8, ptrsize=8, doublesize=8, byteorder=12345678
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=16
    ivtype='long', ivsize=8, nvtype='double', nvsize=8, Off_t='off_t', lseeksize=8
    alignbytes=8, prototype=define
  Linker and Libraries:
    ld='llvm-gcc-4.2 -mmacosx-version-min=10.7', ldflags ='-arch x86_64 -arch i386 -fstack-protector -L/usr/local/lib'
    libpth=/usr/local/lib /usr/lib
    libs=-ldbm -ldl -lm -lutil -lc
    perllibs=-ldl -lm -lutil -lc
    libc=, so=dylib, useshrplib=true, libperl=libperl.dylib
    gnulibc_version=''
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=bundle, d_dlsymun=undef, ccdlflags=' '
    cccdlflags=' ', lddlflags='-arch x86_64 -arch i386 -bundle -undefined dynamic_lookup -L/usr/local/lib -fstack-protector'


Characteristics of this binary (from libperl): 
  Compile-time options: MULTIPLICITY PERL_DONT_CREATE_GVSV
                        PERL_IMPLICIT_CONTEXT PERL_MALLOC_WRAP USE_64_BIT_ALL
                        USE_64_BIT_INT USE_ITHREADS USE_LARGE_FILES
                        USE_PERLIO USE_PERL_ATOF USE_REENTRANT_API
  Locally applied patches:
    /Library/Perl/Updates/&lt;version&gt; comes before system perl directories
    installprivlib and installarchlib points to the Updates directory
  Built under darwin
  Compiled at Jun 13 2011 14:45:31
  %ENV:
    PERLBREW_HOME="/Users/clt/.perlbrew"
    PERLBREW_PATH="/Users/clt/perl5/perlbrew/bin"
    PERLBREW_ROOT="/Users/clt/perl5/perlbrew"
    PERLBREW_VERSION="0.27"
  @INC:
    /Library/Perl/5.12/darwin-thread-multi-2level
    /Library/Perl/5.12
    /Network/Library/Perl/5.12/darwin-thread-multi-2level
    /Network/Library/Perl/5.12
    /Library/Perl/Updates/5.12.3
    /System/Library/Perl/5.12/darwin-thread-multi-2level
    /System/Library/Perl/5.12
    /System/Library/Perl/Extras/5.12/darwin-thread-multi-2level
    /System/Library/Perl/Extras/5.12
    .
Vigor14:~ clt$ 


Just compiled perlbrew with the new Xcode (downloaded from the AppStore):

Vigor14:~ clt$ perlbrew install perl-5.14.1
Fetching perl-5.14.1 as /Users/clt/perl5/perlbrew/dists/perl-5.14.1.tar.gz
Installing /Users/clt/perl5/perlbrew/build/perl-5.14.1 into ~/perl5/perlbrew/perls/perl-5.14.1

This could take a while. You can run the following command on another shell to track the status:

  tail -f ~/perl5/perlbrew/build.log

Installed /Users/clt/perl5/perlbrew/build/perl-5.14.1 as perl-5.14.1 successfully. Run the following command to switch to it.

  perlbrew switch perl-5.14.1


compiler:

Vigor14:~ clt$ gcc -v
Using built-in specs.
Target: i686-apple-darwin11
Configured with: /private/var/tmp/llvmgcc42/llvmgcc42-2335.15~25/src/configure --disable-checking --enable-werror --prefix=/Developer/usr/llvm-gcc-4.2 --mandir=/share/man --enable-languages=c,objc,c++,obj-c++ --program-prefix=llvm- --program-transform-name=/^[cg][^.-]*$/s/$/-4.2/ --with-slibdir=/usr/lib --build=i686-apple-darwin11 --enable-llvm=/private/var/tmp/llvmgcc42/llvmgcc42-2335.15~25/dst-llvmCore/Developer/usr/local --program-prefix=i686-apple-darwin11- --host=x86_64-apple-darwin11 --target=i686-apple-darwin11 --with-gxx-include-dir=/usr/include/c++/4.2.1
Thread model: posix
gcc version 4.2.1 (Based on Apple Inc. build 5658) (LLVM build 2335.15.00)