Debian has decided to enable developers to have more than one Perl on their system. You can have perl-5.004 and perl-5.005. However only one version of Perl will be officially blessed at a time. This official version should be used to build all Perl modules. The current policy is to bless the more recent Perl available in Debian. The official Perl will always be available under /usr/bin/perl. Older Perls will be available as /usr/bin/perl-$version.
This choice has many consequences on how modules and Perl itself are packaged. You'll find all the details in the following chapters.
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