or download this
perl -le 'print unpack("N", pack("H8",substr("0"x8 . "641e0100",-8)));
perl -le 'print unpack("N", pack("H8",substr("0"x8 . "641e0100",-8)));
+'
...
perl -e "print unpack('h', '0x641e0100')"
perl -e "print unpack('h*', '0x641e0100')"
perl -e "print pack('h*', '0x641e0100')"