use strict;
use warnings;

sub d {
    my $n = unpack 'B*', shift;

    my $s = substr($n, 0, 1, '') ? '-' : '';
    my $e = oct('0b' . substr($n, 0, 11, ''));
    (my $m = $n) =~ s/(.{4})/uc unpack 'H', pack 'B4', $1/eg;

    if ($e == 0) {
       return "denormal ($m)" if $m =~ /[^0]/;
       return $s . '0';
    }

    elsif ($e == 0x7FF) {
       return "NaN ($m)" if $m =~ /[^0]/;
       return $s . 'inf';
    }

    $e -= 0x3FF;

    return $s . '1.' . $m . ' * 2**' . ($e < 0 ? "($e)" : $e);
}


my $line = 0;
for (
    'Merry Ch',
    'Kerry Ch',
    'ristmas!',
    'tistmas!',
) {
    print("\n") if $line && $line % 2 == 0;
    ++$line;

    # This program requires a little-endian machine.
    my $pd = reverse $_;

    printf("%s  %s = %s\n",
        $_,
        uc(unpack('H*', $pd)),
        d($pd),
    );
}
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