Some more information on this (which was shown to you when you finished `make install` ;)

Installation of Perl distribution is finished.  Please note, that since
Perl is also in the base system, this distribution will not be used by
default.

If you want this version of Perl to be used by default, please type

  use.perl port

Assuming that use.perl script (which was installed with the rest of the
Perl distribution) can be found in your PATH (you might have to type
`rehash' first, depending upon a shell you use), this action will
replace /usr/bin/perl and /usr/bin/suidperl with symbolic links to the
versions of these binaries in the Perl distribution.  This action will
also put some variables into your /etc/make.conf file, so that newly
installed ports (not packages!) will use new version of perl, and the
system upgrades from the source will not overwrite the changes made.

At any time you can also type

  use.perl system

if you wish to revert back to the system version of perl.