I can't tell if you are using the right algorithm, but here my little implementation inside the debugger.

Please note

• how I avoid operating on strings, except for input and output.
• that it doesn't matter if the input numbers are shown in decimal or hex.

 
  DB<96> x @input = map {ord} split //,'202005'  # input ASCII values
0  50
1  48
2  50
3  48
4  48
5  53
  DB<97> $result = 0                           ; # neutral start

  DB<98> $result ^= $_ for @input              ; # XOR all

  DB<99> p $result
5
  DB<100> p $result2 = int( $result / 0x10 )
0
  DB<101> print "Input: "; printf "0x%x ",$_ for @input
Input: 0x32 0x30 0x32 0x30 0x30 0x35
  DB<102> printf "Output: 0x%x", $result2
Output: 0x0
[download]

NB: in case you adopt this code:

• p and x are debugger commands for dumping results, please ignore them.
• please declare the variables with my (debugger can't handle them)
• one doesn't need to decompose a string for input

   DB<105> x @input = (0x32, 0x30, 0x32, 0x30, 0x30, 0x35)
  0  50
  1  48
  2  50
  3  48
  4  48
  5  53
  [download]

• If you want to operate on large sets of data consider using unpack and pack to initalize the input

HTH!

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