I strongly recommend you Use strict and warnings, it will lead to cleaner code in general.

Your data seems to me to be better suited in a hash, e.g.

use warnings;
use strict;

my %pizzas = (
    pizza_margherita => 'pizza_margherita',
    cheese => 'cabrales',
    tomato => 'orlando',
    mass => 'secret',
    USERNAME => $ENV{USERNAME},
);

for my $key (keys %pizzas) {
    print "$key=$pizzas{$key}\n";
}

__END__
# Output:

USERNAME=foo
pizza_margherita=pizza_margherita
mass=secret
cheese=cabrales
tomato=orlando
[download]

To answer your direct question: that is possible with symbolic references or eval, but I wouldn't recommend using either of those because they are advanced techniques that should only be used sparingly and only when you know their use is appropriate, and this doesn't seem like one of those cases, unless you can explain why it is.