pack and unpack are useful tools for generating strings of bytes for interchange and extracting values from such strings respectively. What follows is a 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");
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Notes:

• < 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 and 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.)