pack and unpack are useful tools for generating strings of bytes for interchange and extracting values from such strings respectively. What follows are two table that represents the relevant formats in a convenient form.

Category	Type		Byte Order			Mnemonic
			Native	Little-Endian (<)	Big-Endian (>)
Fixed-Size Integers	8-bit integer	Unsigned	C			"C" for char
		Signed	c
	16-bit integer	Unsigned	S	S< or v	S> or n	"S" for short
		Signed	s	s< or v!	s> or n!
	32-bit integer	Unsigned	L	L< or V	L> or N	"L" for long
		Signed	l	l< or V!	l> or N!
	64-bit integer	Unsigned	Q	Q<	Q>	"Q" for quad
		Signed	q	q<	q>
Types Used By This Build of perl	UV (unsigned integer)		J	J<	J>	"J" is related to "I"
	IV (signed integer)		j	j<	j>
	NV (floating-point)		F	F<	F>	"F" for float
Underlying C Types for This Build of perl	char		—	—	—
	unsigned char		—	—	—
	signed char		—	—	—
	unsigned short int		S!	S!<	S!>	"S" for short
	signed short int		s!	s!<	s!>
	unsigned int		I! or I	I!< or I<	I!> or I>	"I" for int
	signed int		i! or i	i!< or i<	i!> or i>
	unsigned long int		L!	L!<	L!>	"L" for long
	signed long int		l!	l!<	l!>
	unsigned long long int		—	—	—
	signed long long int		—	—	—
	float		f	f<	f>	"f" for float
	double		d	d<	d>	"d" for double
	long double		D	D<	D>	A bigger double

For the pointers used by this build of perl, you can use the following:

use Config qw( %Config );

use constant PTR_SIZE => $Config{ptrsize};

use constant PTR_PACK_FORMAT =>
     PTR_SIZE == 8 ? 'Q'
   : PTR_SIZE == 4 ? 'L'
   : die("Unrecognized ptrsize\n");
[download]

Notes:

• There is more than one way to store signed integers. I believe that Perl only runs on machines that use two's complement for signed integers, so "Signed" refers to this format.
• < and > indicate byte order. The small end of the bracket is at the least significant end of the number. (< for little-endian byte order, and > for big-endian byte order.) Can't be used with N/n and V/v.
• For integers, ! signifies using the C types of this build of perl. Exception: N/n/V/v.
• For integers, uppercase indicates unsigned, and lowercase indicates signed. Exception: N/n/V/v.
• N and n are used for network (i.e. internet) byte order (BE), with the uppercase letter being used for the larger bitsize.
• V and v are used for VAX byte order (LE), with the uppercase letter being used for the larger bitsize.
• Using Q/q requires a Perl with 64 bit integers.
• Unsupported types:
  • unsigned long long int (Q! would be an obvious choice for it.)
  • signed long long int (q! would be an obvious choice for it.)
  • char
  • unsigned char (C! would be an obvious choice for it.)
  • signed char (c! would be an obvious choice for it.)

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