my $base = $feed_opts->{url};
my $mid = mid_clean($header_obj->header('Message-ID'));
$mid = uri_escape_utf8($mid);
- my @archived_at = $header_obj->header('Archived-At');
- push @archived_at, "<$base$mid/>";
- $header_obj->header_set('Archived-At', @archived_at);
- $header_obj->header_set('List-Archive', "<$base>");
- $header_obj->header_set('List-Post', "<mailto:$feed_opts->{id_addr}>");
+ my %append = (
+ 'Archived-At' => "<$base$mid/>",
+ 'List-Archive' => "<$base>",
+ 'List-Post' => "<mailto:$feed_opts->{id_addr}>",
+ );
+ while (my ($k, $v) = each %append) {
+ my @v = $header_obj->header($k);
+ foreach (@v) {
+ if ($v eq $_) {
+ $v = undef;
+ last;
+ }
+ }
+ $header_obj->header_set($k, @v, $v) if defined $v;
+ }
my $buf = $header_obj->as_string;
unless ($buf =~ /\AFrom /) {