$a = 1;
$a = 2;
print "\$a is $a\n";

$a[0] = 1;
$a[0] = 2;
print "\$a[0] is $a[0]\n";

$a{key} = 'value';
$a{key} = 'newvalue';
print "\$a{key} = $a{key}\n";