If you have more than ten or twenty fields (whose format I usually cut 'n paste from some document), I find the explicit use of unpack unmanagable (e.g. adding/deleting, or changing the length of a field in the middle of the format is a pain, e.g. when there's a typo in the doc or the doc includes 'sub-fields' which are not obvious), and I like to use Parse::FixedLength, which for your example would be:

my $parser = Parse::FixedLength->new([qw(
  first:2
  second:4
  filler:4
  third:4
)]);
my $href = $parser->parse($line);
print "$href->{first}\n";
etc.
[download]