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