./foobar.pl # <- perl from shebang
perl foobar.pl # <- whatever perl is found first in $ENV{'PATH'}
/home/me/bin/perl-special foobar.pl # <- a special perl
/usr/local/bin/perl foobar.pl # <- common location for a local perl
/usr/bin/perl foobar.pl # <- common location for system perl

##</code><code>##

#!/usr/bin/env perl

use 5.014;
use strict;
use warnings;