Replace

    (1 x $str2), (1 x (32 - $str2))
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with

    (1 x $str2) . (0 x (32 - $str2))
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B32 want a string of 32 characters (preferably where each character is "0" or "1"). When you give it a string of fewer than 32 chars, then it assumes "0"s for the missing chars. Your second string is simply being ignored.