Hmm. That's an interesting result. Can you give me the output of

print join(" ", map { sprintf "%#02x", $_ }
    unpack("C*",pack("L",0x12345678))), "\n";
[download]

on your system? XS won't be possible, by the way, as this is intentionally a pure-perl implementation.

sure 0x78 0x56 0x34 0x12

    $ perl -le 'print unpack "H*", reverse pack "f", 440'
    43dc0000

    $ perl -le 'print unpack "H*",         pack "f", 440'
    0000dc43
[download]

--
John.