I agree with you. According to your idea, users don't need to pass a reference subroutines on every call:

use Blosxom::Header;

# procedural interface
my $value = Blosxom::Header->get($key);
my $bool  = Blosxom::Header->exists($key);
Blosxom::Header->set($key => $value);
Blosxom::Header->remove($key);

# OO interface
my $h     = Blosxom::Header->new();
my $value = $h->get($key);
my $bool  = $h->exists($key);
$h->set($key => $value);
$h->remove($key);
[download]

Nobody uses my module except for me :) But I belive this module should exist.

Update:

I noticed that it's not necessary to implement OO interface any more in this case.