my $item = { 
    char => 'df',
    secs => 65,
    version => 4,
    misc => 'data',
    data => 'misc'
    };

# access with
$item->{char} = 'ef';
# the print you asked for, outputs 0x0041
printf ("0x%04x", $item->{secs});

# what do you mean binary 0's? something like this?
my @array = ("\000") x 10000;