The documentation for pack() goes into this is some detail. You should read perldoc -f pack. For example, it says:

The integer formats `s', `S', `i', `I',
`l', and `L' are inherently non-portable
between processors and operating systems
because they obey the native byteorder and
endianness.  For example a 4-byte integer
0x12345678 (305419896 decimal) be ordered
natively (arranged in and handled by the
CPU registers) into bytes as

        0x12 0x34 0x56 0x78     # little-endian
        0x78 0x56 0x34 0x12     # big-endian

Basically, the Intel, Alpha, and VAX CPUs
are little-endian, while everybody else,
for example Motorola m68k/88k, PPC, Sparc,
HP PA, Power, and Cray are big-endian.
MIPS can be either: Digital used it in
little-endian mode; SGI uses it in big-
endian mode.
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And it runs onward, into the sunset...

Paris Sinclair    |    4a75737420416e6f74686572
pariss@efn.org    |    205065726c204861636b6572
I wear my Geek Code on my finger.