#!/usr/bin/perl -w


use strict;

my $hexvalue = $ARGV[0];
print unpack "L<", pack "H*", $hexvalue;
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Obviously it returned another decimal value.

For the same input, it should return the same on every machine, including your PowerPC.

Or let it run a function as being a in little-endian environment?

Since endianness only matters when you're talking about how something is stored and you can't access the buffers in which Perl stores its numbers, there's no way to be affected by endianness used. Your request makes no sense.

absolutely...there's no way for a program to magically work out if a number is big or little endian. So the script somehow has to know that and use the appropriate kind of pack/unpack. or you could even just swap half the string around using string manipulation, before coalescing to decimal. either way it has to be known which way the endian goes. if these numbers are some well known numbers (say serial numbers for a computer product) then they usually already have some logic encoding to them, which could give you a clue. e.g. leftmost decimal 4 digits a valid vendor code in a known list, etc.
the hardest line to type correctly is: stty erase ^H