Without reading the docs, my guess is that perl handles it. Either by leaving the scope or by assigning something else to the variable containing the object.

do {
    my $pdf=CAM::PDF->new(...);
    $pdf->foo();
    $pdf->bar();
}; # object destroyed by perl
[download]

my $pdf=CAM::PDF->new(...);
$pdf->foo();
$pdf->bar();
$pdf=''; # object destroyed by perl
[download]

Alexander