The easiest way to copy the Perl 5 repository is to use git:
git clone git://perl5.git.perl.org/perl.git perl
A mirror of the repository is found at https://github.com/Perl/perl5. The master branch, where the development takes places, is named blead. The maintenance branches are named perl-5.XXX depending on the maintenance version.
For people who can't or don't want to use git, the latest sources are also available through rsync:
rsync -avz rsync://perl5.git.perl.org/APC/perl-current .
or, for the maintenance branches:
rsync -avz rsync://perl5.git.perl.org/APC/perl-5.10.x . rsync -avz rsync://perl5.git.perl.org/APC/perl-5.8.x .
For more details on working with the Perl source code, please see the perlhack documentation.
If you are interested in released versions of perl, you can download them from the CPAN Perl Source Code page.