#! /usr/bin/perl 
use Readonly;

Readonly my $vars => { X => 20, Y => 20 };
Readonly my $eq => [ 2 * Y, -2 * X * Y ];

$x = $vars->{X};
$y = $vars->{Y};
print "Val of \$x is $x \n";  # print 20
print "Val of \$y is $y \n";  # print 20

$temp = $eq->[0];
print "$temp \n"; # print 0

print $eq->[1] . "\n"; print 0

##</code><code>##

print "$temp \n"; 
# and
print $eq->[1] . "\n";

##</code><code>##

Readonly my $eq => [ 2 * $vars->{Y}, -2 * $vars->{X} * $vars->{Y} ];
### instead of
Readonly my $eq => [ 2 * Y, -2 * X * Y ];

##</code><code>##

print "$temp \n";   ## prints 40
# and
print $eq->[1] . "\n";  ## prints -800