When an object is destroyed (garbage collected), its DESTROY method is called.

{
    package Some::Class;
    sub new {
        my $self = bless {}, shift;
        print "Object created.\n"; 
        return $self;
    }
    sub DESTROY {
        print "Object destroyed.\n"; 
    }
}

print "1\n";
for (1 .. 3) {
    print "2\n";
    my $foo = Some::Class->new;
    print "3\n";
}
print "4\n";
__END__
1
2
Object created.
3
Object destroyed.
2
Object created.
3
Object destroyed.
2
Object created.
3
Object destroyed.
4
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You can tie a variable to an object.

use Tie::Scalar;
{
    package Some::Class;
    our @ISA = qw(Tie::StdScalar);
    sub DESTROY {
        print "Object destroyed.\n"; 
    }
}

if (1) {
    print "1\n";

    # my $foo = 3;
    tie my $foo, 'Some::Class';
    $foo = 3;

    print "2\n";
}
print "3\n";

__END__
1
2
Object destroyed.
3
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