After a bit of RTFM-ing, reading the source and experimenting, I think the %matchspec is supposed to be used something like this: 

use LWP::UserAgent qw( );

my $ua = LWP::UserAgent->new();
my $url = 'http://www.google.com/';
my $resp;

$resp = $ua->get($url); print($resp->status_line(), "\n");
show(1);
print("Added:\n");
$ua->add_handler( response_header => sub { print "HANDLER\n"; }, owner
+ => "myfunc");
show(2);
$resp = $ua->get($url); print($resp->status_line(), "\n");
show(3);
print("Removed:\n");
$ua->remove_handler('response_header', owner => "myfunc");
show(4);
$resp = $ua->get($url); print($resp->status_line(), "\n");
show(5);

sub show {
  print(join(" ", @_, $ua->handlers('response_header', $resp)), "\n");
}

__END__
200 OK
1 HASH(0x8c2440)
Added:
2 HASH(0x8c2440) HASH(0x93b0e0)
HANDLER
HANDLER
200 OK
3 HASH(0x8c2440) HASH(0x93b0e0)
Removed:
4 HASH(0x8c2440)
200 OK
5 HASH(0x8c2440)

[download]

where "myfunc" is some self-chosen name that you use to identify the callback for removal.

(When you dump the hashes, you can see that the one associated with the internal handler (HASH(0x8c2440)) has owner => 'LWP::UserAgent::parse_head')

As you can see, the internal callback remains intact this way.

In reply to Re^3: LWP handlers examples? by almut
in thread LWP handlers examples? by vitoco

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