use strict;
use warnings;

my $record;

while ( <DATA> ) {
  next if /^\s*<!--/;
  next if /^\s*$/;

  $record       = { TYPE => $1 }, next if /<object/   and /type="([^"]*)"/;
  $record->{$1} = $2,             next if /<property/ and /name="([^"]*)"\s+value="([^"]*)"/;

  if ( /<\/object/ ) { # flush current record
    ( print join(',', map { $record->{$_} // 'n/a' }
		 qw(name dog_breed_id dog_breed_name)),"\n"
    ) if $record->{TYPE} eq 'Dog';
    $record = undef; # not really necessary
    next;
  }

  warn "Unexpected input (line $.): $_";
}


__DATA__
  <!-- Dog section -->

  <object type="Dog" >
    <property name="id" value="0" />
    <property name="name" value="REX" />
    <property name="status" value="alive" />
    <property name="mode" value="owned" />
    <property name="dog_breed_id" value="0" />
    <property name="dog_breed_name" value="Husky" />
    <property name="capacity" value="105" />
    <property name="size" value="big" />
    <property name="location" value="canada" />
  </object >

  <object type="Fish" >
    <property name="id" value="8" />
    <property name="name" value="Ginger" />
    <property name="status" value="alive" />
    <property name="mode" value="owned" />
    <property name="fish_breed_id" value="4" />
    <property name="fish_breed_name" value="Guppy" />
    <property name="capacity" value="105" />
    <property name="size" value="big" />
    <property name="location" value="glassbowl" />
  </object >

  <object type="Dog" >
    <property name="id" value="9" />
    <property name="name" value="Norbert" />
    <property name="status" value="alive" />
    <property name="mode" value="owned" />
    <property name="dog_breed_id" value="7" />
    <property name="dog_breed_name" value="Norwegian Wolf" />
    <property name="capacity" value="105" />
    <property name="size" value="big" />
    <property name="location" value="norway" />
  </object >

  <comment value="This should trigger a warning..." />

##</code><code>##

EX,0,Husky
Norbert,7,Norwegian Wolf
Unexpected input (line 39):   <comment value="This should trigger a warning..." />