A victim object with a destructor can be your instructor. 

package Canary;

sub new { return bless {}, shift(); }
sub DESTROY { warn "*CHEEP* *GASP*"; }

package main;

END { warn "END BLOCK\n"; }

$| = 1;

my $closure;
{
  my $boid = Canary->new();
  $closure = sub { $boid = $boid; warn "Fweee\n"; };
}
$closure->();

warn "Pre undef\n";
undef $closure;
warn "Post undef\n";

exit 0;

__END__
$ perl spoozle
Fweee
Pre undef
*CHEEP* *GASP* at spoozle line 4.
Post undef
END BLOCK

[download]

The cake is a lie.
The cake is a lie.
The cake is a lie.

In reply to Re: When are references within a closure freed? by Fletch
in thread When are references within a closure freed? by Socrates

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