Corion is right that if there is an appropriate module to do this for you, you should use that. <update> For example as VinsWorldcom demonstrated here. </update>

If it turns out you do need to do this yourself, here are two ideas based on unpack (templates explained in perlpacktut and pack) and regexes. The first is a little more robust in its parsing, the second a little shorter and simpler.

my $data = "\000\012\000\144\023\304\003pbx\007example\003com\000:3600
+";

my ($pri,$weight,$port,$rest) = unpack "S>3A*", $data;
my $target='';
$target .= (length($target)?'.':'').$2
    while $rest=~/\G([\x01-\xFF])((??{".{".ord($1)."}"}))/saagc;
my ($ttl) = $rest=~/\G\x00:(.+)\z/saagc or die "failed to parse";

# - OR -

my ($pri,$weight,$port,$target,$ttl) = unpack "S>3Z*A*", $data;
$target = join '.', unpack "(C/A)*", $target;
$ttl=~s/\A://;
[download]