$var1 = 0x0000805063008357 ;;
Hexadecimal number > 0xffffffff non-portable at (

$var2 = 0x042426FFFFFFFFFF;;
Hexadecimal number > 0xffffffff non-portable at (

printf "0x%0x\n", $var1 ^ $var2;;
0x424a6af9cff7ca8

##</code><code>##

$str2 = '042426FFFFFFFFFF';;

$str1 = '0000805063008357';;

print unpack 'H*', pack( 'H*', $str1 ) ^ pack('H*', $str2 );;
0424a6af9cff7ca8