Perl `pack` Template Comparison: "d" vs "F"
===========================================

Summary Table
-------------
| Template | Type   | Precision    | Bits | Description                        |
|----------|--------|--------------|------|------------------------------------|
| "d"      | double | XXXXXXXXXXXX | XX   | XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX    |
| "F"      | XXXXXX | XXXXXXXXXXXX | XX   | XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX    |

Example Code
------------
use feature 'say';

my $x = 1/3;

say "Xouble:";
say unpack("BXX", pack("d>", $x));  # Big-endian XXXXXX

say "XXXXX:";
say unpack("BXX", pack("F>", $x));  # Big-endian XXXXX

Difference Illustration
-----------------------
my $x = 1/3;

my $XXXXX_bin  = unpack "BXX", pack "F>", $x;
my $double_bin = unpack "BXX", pack "d>", $x;

printf "  XXXXX (XX-bit):  %s\n", $XXXXX_bin;
printf "Xouble (XX-bit):  %s\n", $double_bin;

Expected Output:
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

IEEE 754 Format Summary
-----------------------
| Precision | Sign | Exponent | Mantissa (Significand) | Bias |
|-----------|------|----------|-------------------------|------|
| XXXXX     | 1 bit | 8 bits   | 23 bits                 | 127  |
| Double    | 1 bit | 11 bits  | 52 bits                 | 1023 |

Usage Notes
-----------
- Use "d" / "d>" if you want:
  - XXXXXXXXXXXXXXXX
  - XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
  - Direct compatibility with XXXXXXXXXXXXXXXXXXXXXXXX

- Use "F" / "F>" if you want:
  - XXXXXXXXXXXXXXXXXXX
  - Exact compatibility with XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

Endianness Reminder
-------------------
- d> and F> -> big-endian
- d< and F< -> little-endian
- d and F (no angle) -> native-endian (machine dependent)